It really comes down to if you want to play or do you want to look up rules.
Fantasy Grounds stores all the data for AC/Saves/To Hits/Damage. So that all you do is click a button and it handles all the calculations for you. Does he have cover? Are you blinded? Do they have blur up? Better remember all that in Roll20 because it wont. Fantasy Grounds will store all that for you so it just comes down to clicking a button while you have your target selected.
The major costs for both are the books and modules, which Fantasy Grounds typically offers for cheaper (Avernus on Roll20 is 49.95 — Avernus on Fantasy Grounds is 29.95) If you’re worried about price, the subscription is slightly higher on Fantasy Grounds ($8.33 Roll20 / $9.99 FG) a month for the DM and the rest play for free. But the ongoing costs are much cheaper on Fantasy Grounds. In addition, only Fantasy Grounds offers a buy once option. If I had paid Roll20 a subscription for as long as I’ve had Fantasy Grounds It would have cost me just under $1400 versus $150 I paid once for Fantasy grounds and I would still be paying Roll20. That’s not modules, or rules, it’s just the amount I would have to pay just to use the full software.
But Here’s a guy that has hundreds of hours in each, and he does a pretty good job of comparing the two. He mentions that Roll20 has dynamic lighting and and automatic fog of war, but Fantasy Grounds has that in their new product Fantasy Ground Unity which just went into Open Beta today. The new Fantasy Grounds will be the same subscription cost as the current. Just cancel one and start the other, it’s backwards compatible so all the modules you bought for this version will work in the next.
I would also take a loot at his other videos and see his other reviews of Roll20 and Fantasy Grounds. He also reviews D&D Beyond.
People that claim that fantasy grounds is more expensive than Roll20, simply haven’t done their research. Roll20 gives you a dollar off on subscription and then charges you near double for everything else.
In addition, any claim that Fantasy Grounds requires you to buy the resources and doesn’t allow you to load your own, such as maps or tokens is incorrect. You can build everything yourself in Fantasy Grounds. Load a map, some tokens and go. You don’t get the automation FG is best at, but even that you can plug in yourself. But, you aren’t limited to just bought rules and modules. We have used FG since this group in OTG was first formed in 2010 and back then there weren’t any purchased rulesets. They were all made by fans. So, you certainly can make your campaign from scratch. Most of the VTT group of OTG have been doing it for 14 years.
If all you want is something to use for a one-shot weekend, Roll20 will suffice. But, if you’re really looking to make this a long-term hobby, Fantasy Grounds will do more and save you money, and has a new version in final testing that will cost the same amount. If you find you like FG, then wait for FGU to be released and buy it flat out. No more subscription payments. Roll20 can’t say that.