Virtual Tabletops are online platforms which provide a suite of tools for a group to play a tabletop game. Mostly these platforms are aimed at Role Playing Game (RPG) players, but many of them could equally be used for playing board games.
The text in this article is taken from this Google Doc which appeared at the beginning of the Coronavirus pandemic.
Usually VTTs include at the least boards (“battle maps”), dice rolling capabilities, chat and character sheets. They often have other fancy features, like dynamic lighting, fog of war, sound effects, add-ons and rules compendiums for popular role playing games.
VTTs may seem like the go-to option for playing RPGs online, yet they have problems. You know the old saying, “Jack of all trades, master of none”? That describes most VTTs. So, by gaining the convenience of only needing one tool, you often lose quality in all the smaller tools that it provides.
Roll20
The biggest player in the VTT game. You can find a million reviews and lists of its features online.
Astral Tabletop
The best VTT for casual D&D players (the average Roll20 user!)
Cost : Freemium $ Complexity : Low User-Friendly : High Learning Curve : Low Platform: Online
For past Roll20 Plus or Free users who play D&D 5e, Astral tabletop is exactly what you want! Astral does almost everything Roll20 does and some things better, but only for D&D. It will take you a little while to get used to the UI, but in the end it’s actually much easier on the eyes than Roll20.
I would also recommend Astral Tabletop for GM’s looking for an easy-to-use, free map-making tool, even if they don’t use the program as a VTT for their games. The maps are export-able.
Pros
Best map-builder in any VTT, with easy to use layers, dynamic lighting, and fog-of-war. Maps can be edited in real time during games!
Built-in video conferencing
Built-in 5e SRD Compendium, with the ability to create and upload your own compendiums
Lower price subscription model (vs Roll20)
A lot of Roll20-like functionality, all for free, dynamic lighting included.
Nice-looking, user-friendly UI. Better text editor than Roll20 ever had.
Easy to learn, which is good for new players.
Entirely online! No software download required. Works on linux, chromebook, and tablets. Cons
Can’t handle games other than D&D yet, though support for other games is on the roadmap.
D&D books are not available for purchase on the platform. Considering the advent of D&D Beyond before this product’s creation, it’s likely they never will be.
Little to no extensibility via scripts, addons, extensions, etc.
Character sheets offer little in the way of automation or customizability, though they have basic macro c apabilities.
No Card, no benny management (Savage Worlds)
Technically “not looking to compete with Roll20”?
Astral left bugs untouched and went effectively dark between 1st release and their new (2nd) release. So Support isn’t ideal, and development/feature develop is spotty (waterfall)
Fog of war is dependent on the dynamic lighting system. Secret doors are very difficult to make.
FoundryVTT
The best platform for ex-Pro DMs.
Cost : $$(GM) Complexity : Medium User-Friendly : Medium Learning Curve : Medium Platform: Mixed
For technically savvy Roll20 GMs, or FG users that didn’t like the learning curve Foundry is for you. Players connect with only a browser. DMs have the software and run a server. Foundry does much of what Roll20 does and some of what Astral does, and often does more - and does it in a less confusing manner, and with a better UI than Fantasy Grounds. All while giving you the ability (if you are code friendly) to tweak or make your own modules for the Foundry platform (ie more control than Astral and Roll20)
I would also recommend FoundryVTT for GM’s looking for alooking a roll20 alternative if they are technically savvy and are willing to provide feedback to improve it.
Pros
Best exposed API library. Treats the gGaming table as a platform and allows the community to build their own games, add- ons (called modules), and the like to work with the core functionality.
Ability to create and upload your own compendiums.
Lower price model (vs Roll20 and FG)
GM pays once (Players don’t pay)
No Paygate, a one- time fee and all features/updates are included. (A lot of Roll20-like functionality already exists).
DM or VPS hosted - so, relatively unlimited storage space and control. (You get the software, you decide how and when you’re running it.)
Players have no clients, they only need to use a browser.r
Sound events (like dynamic lighting, but for sound).
Linked mMaps and togglable dDoor openings.
Supports Animated tokens & maps.
Development is highly communicative/respo and speedy.
Excellent wikiWIKI for setup/support and community contribution.to bring such.)
Exceptional cCard/rRollable table system
Incredibly extendable library of Mods (what they call modules) that range from Theme changes; to direct integration of Discord for chat and audio/video conferencing; to adding token creation similar to TokenTools.
Built-in 5e SRD Compendium, with the ability to create and upload your own compendiums Cons
It’s in Beta. While it’s playable right now, the code isn’t fixed and the dataand data schema may still change, so. (So your customization/importing may need to be updated).
D&D books are not available for purchase on the platform, nor are any other gaming systems. It has no marketplace. Note: Content from D&D Beyond/ Roll20 can be imported/used through community- provided extensions (called modules within Foundry VTT).
5e Character sheets areis a bit kludgy still.
Single developer. If they lose interest, the project may not be maintained/further updated.
If the game master is not actively running the server, players have no access to their character, the compendium, or, and their data (currently).
Very few game systems are currently supported, and new systems are developed by the community (D&D 5e; Starfinder; Pathfinder; Warhammer 4e; Pathfinder 1st & 2e; Savage Worlds; Starfinder; Fate; 13th Age as of 12/27/2019).
No current content Encryption; so it’s likely that larger partnerships with WoTC are not going to be in place at launch; but relationship with World Anvil; DungeonFog; DunGen; Iron Moose; Forgotten Adventures
Fantasy Grounds
A good fit for ex-Roll20 Pro users and tinkerers.
Cost : $ Complexity : High User-Friendly : Med Learning Curve : High Platform: Server
For past Roll20 Pro users, this is probably your first choice. If you used API scripts a lot in Roll20 and liked being able to automate as much of your game as possible, Fantasy Grounds is for you. Fantasy Grounds is also best suited for certain popular games (see the front page of their site,) though the community supports many other RPGs to varying degrees. FG is a VTT-tinkerer’s playground, for a price that is potentially less than or at most equal to a Roll20 pro subscription.
I would argue that FG is not a good Roll20 replacement for Plus or Free users, however. Not only is it more expensive than those Roll20 tiers, but it offers a level of complexity that most casual Roll20 users will probably find daunting and unnecessary for the kind of play they are comfortable with.
Pros
D&D, Pathfinder, Starfinder, Savage Worlds, and more are baked in with support for all books
Available for subscription or a one time only fee. If the GM gets Ultimate, players don’t have to pay.
Nearly everything can be automated, from dealing damage to spell effects
Neat features like 3D dice, chat languages, quest tracking, and party inventory.
Very involved community that creates content and builds extensions to add almost any feature you could possibly want.
One-stop shop for all your needs — character sheet, rolling, chatting, inventory, random generators, books, map sharing, and gm prep.
D&D books are less expensive on FG than on Roll20, and even less expensive than that if you know where to look. 
Integrated with DM’s Guild, with many 3rd party adventures offered in ready-to-go, FG format.
Heavily automated. Lot of things are handled for you. Durations of status effects, taking wounds.
Doesn’t require a browser for use. Cons
Very steep learning curve, especially for GMs. FG is incredibly powerful, and with complexity to accommodate that power.
No dynamic lighting, only Fog of War.
Expensive — Standard ($3.99/$39.99 per player) or Ultimate ($10/150 GM-gm only) licenses.
Unfriendly, dated UI — plagued with window clutter, bad text editing capabilities, low resolution. Best used in full screen, so not awesome for tables that utilize other software during play or small laptop screens.
Map editing capabilities are minimal at best.
Manipulating maps can be difficult. Map and token controls are somewhat less than user-friendly.
No baked-in audio/video conferencing abilities.
Heavily automated. You have to declare all bonus before hand. Hard to add custom stuff (requires “coding”). Hard to rule something differently on the fly (e.g. ignore a very high roll from a mob that would kill an NPC, or ignore a third fumble in a row from your main boss just to make things interesting!)
Requires players to install client and some moderate knowledge of how to bypass firewalls potentially to get connectivity between DM and player’s PC client. WHICH means, change machines, … you need to do that install dance again. Versus browser to centralized server/service
Note: Not for 4k screens.
Fantasy Grounds UNITY
A good fit for ex-Roll20 Pro users and tinkerers.
Cost: $ Complexity: High User-Friendly: Med Learning Curve: High Platform: Server
For past Roll20 Pro users, this is probably your first choice. If you used API scripts a lot in Roll20 and liked being able to automate as much of your game as possible, Fantasy Grounds is for you. Fantasy Grounds is also best suited for certain popular games (see the front page of their site,) though the community supports many other RPGs to varying degrees. FG is a VTT-tinkerer’s playground, for a price that is potentially less than or at most equal to a Roll20 pro subscription.
I would argue that FG is not a good Roll20 replacement for Plus or Free users, however. Not only is it more expensive than those Roll20 tiers, but it offers a level of complexity that most casual Roll20 users will probably find daunting and unnecessary for the kind of play they are comfortable with.
Pros
D&D, Pathfinder, Starfinder, Savage Worlds, and more are baked in with support for all books
Available for subscription or a one time only fee. If the GM gets Ultimate, players don’t have to pay.
Nearly everything can be automated, from dealing damage to spell effects
Neat features like 3D dice, chat languages, quest tracking, and party inventory.
Very involved community that creates content and builds extensions to add almost any feature you could possibly want.
One-stop shop for all your needs — character sheet, rolling, chatting, inventory, random generators, books, map sharing, and gm prep.
D&D books are less expensive on FG than on Roll20, and even less expensive than that if you know where to look.
Integrated with DM’s Guild, with many 3rd party adventures offered in ready-to-go, FG format.
Heavily automated. Lot of things are handled for you. Durations of status effects, taking wounds.
Backward compatible with FG
Dynamic Lighting/Fog of War
UNITY engine rebuild
Supports animated maps and map assets (and doesn’t have the memory leaks and crashing issues that FG classic had has. Cons
Very steep learning curve, especially for GMs. FG is incredibly powerful, and with complexity to accommodate that power.
Cost ??
STILL Unfriendly, dated UI — plagued with window clutter, bad text editing capabilities, low resolution. Best used in full screen, so not awesome for tables that utilize other software during play or small laptop screens.
Map editing capabilities are minimal at best. BUT it now supports
Manipulating maps can be difficult. Map and token controls are somewhat less than user-friendly.
No baked-in audio/video conferencing abilities.
Heavily automated. You have to declare all bonus before hand. Hard to add custom stuff (requires “coding”). Hard to rule something differently on the fly (e.g. ignore a very high roll from a mob that would kill an NPC, or ignore a third fumble in a row from your main boss just to make things interesting!)
Note: Not for 4k screens.
MapTool
For tinkerers, fans of open-source, and players of obscure games.
Cost : Free Complexity : High User-Friendly : Low Learning Curve : High Platform: Server
MapTool is in an awkward space here because if it appeals to you, you were probably using it instead of Roll20 in the first place. MapTool fills a lot of the same niches as Fantasy Grounds, but with a much steeper learning curve and a much lower cost ($0).
I would recommend MapTool for ex-Roll20 Pro users who are willing to dive deep to save some money, who also have a table of serious players that are willing to face down an intimidating user experience. I would also recommend it to Roll20 Pro users who want a VTT that can be more easily adapted to play more obscure games.
Pros
Suitable for playing almost any game, even board games and war games.
Free! MapTool is open-source. It will always, forever, be 100% free.
Extremely thorough chat feature, with crazy formatting, bells, whistles, macros, and chat commands galore.
Extremely feature-rich map sharing/editing. Dynamic lighting, fog of war, AOE effects, etc.
Extremely active modding/macro community that can help you automate and add bells and whistles to just about any part of your game.
Extensive tutorials available. Extremely active and helpful community.
Works on linux! Cons
Interface is ugly as sin and possibly better described as user- hostile .
Learning curve is insanely high.
Takes a lot of time to set up for your game of choice.
Requires separate programs or macros for character sheet support and encounter tracking.
Uses Java (may be a drawback for some people.)
No legally available RPG content from popular publishers like WotC and Paizo.
No video chat integration.
D20 Pro
For committed D20 tables with a budget.
Cost : Complexity : Med User-Friendly : Med Learning Curve : Med Platform: Server
I haven’t spent a ton of time with D20 Pro myself, simply because my laptop screen is 4K, and thus the only way I am able to interact with the program is with an interface best suited for ants. However, this is what I could glean from the internet.
D20 Pro has many of the same features as Fantasy Grounds, and it’s growing at a very fast pace. It’s a bit uglier than FG, but much less expensive (though not free for GMs). The community is pretty small, but active enough that it is still useful. I’d still recommend giving it a try.
Pros
Less expensive than FG and Roll20, with a one-time- only price of $50 for a GM license + 4 player seats (additional seats cost $10)
SLIGHTLY Less expensive than FG and Roll20, with a one-time- only price of $50 for a GM license + 4 player seats (additional seats cost $10)
Pretty extensive automation abilities.
5e & PF SRD available for free and PHB and MM available for purchase
Newly implemented extensions abilities.
Custom HTML character sheets provided by the community
Extensive map sharing abilities; dynamic lighting, fog of war, pins, notes, etc.
Works on linux! Cons
Unusual user interface design increases the learning curve.
Best suited for D20 games, though it can technically be used for other RPGs with some elbow grease.
User interface is uglier than fantasy grounds (but nicer than MapTools), with no ability to adjust it with themes.
Requires Java.
Community isn’t super active. Developers very active on discord https://discord.gg/a4mtnm
No integrated video chat.
Note: Not for small or 4k screens.
Mythic Table
Promising, not yet open, newcomernew comer to the VTT scene. No
Pros
Auto resolution with Undo
Open Source (gitlab). So can expect durability and lots of modules/settings/games. Cons
Not yet available.