Superficially they are indeed very similar, you're getting a 3D simulated world with the board game in it, and then a clumsy way to interact with that world.

We did not find (not sure if any exist) rules enforcement implementations for Tabeltopia. Every game we tried we had to understand and enforce any rules, and the physics engine is arguably an obstacle rather than assistance as it neatly allows you to drop cards where they can't go, flip cards you shouldn't see, resize counters or accidentally stack them when that's not useful....

Big upside to Tabletopia: It runs in browser. If a person in your group has a company laptop that's locked down to do Office and so on, chances are it can't run Steam (and so TTS isn't possible) but it can run Chrome and thus Tabletopia works.

Definitely the biggest contrast is to BGA. BGA is the place to go if you want rules enforcement and aren't happy to stick with one game you all enjoy. But you won't get any of the mechanical joy if that's important to you. If you actually enjoy making change with monopoly money, BGA discards that because their rules enforcement just turns the amount of money (cows, glory, mana, whatever) into a number instead. Little wooden cubes become small red squares on the screen that appear exactly where the designer put them, you can't balance them or line them up how you want, because that isn't part of the game rules.

Personally I am now spending several hours every single week on a variety of games at BGA and maybe one session of TTS Gloomhaven if we can face it.

To me video conferencing isn't essential. We usually run a Hangout for live games, but in practice you care mostly about the voices. It's satisfying to hear another player say "Aw, I wanted that" when you take away an option you suspected they wanted, and it's easy to say "Sorry, Jenny is screaming, back in five" and put the headset down compared to having to type all that with a child screaming.