FG is my first choice. The automation is great, especially for more mechanically complex games like PF and SF where you want to track lots of ongoing effects. It has a bit more of a learning curve for things like coding effects, but most stuff is pretty straightforward. It also has great product support from most major game companies so it is very easy to get up an running with published adventures and such.
Roll20 is fine. It has the biggest user base so it is the best platform for finding groups, especially if you are looking for a very specify system or time. It also has great product support and decent tools. However, even having played on it for hundreds of hours, I still find the interface clunky and hard to navigate. Example: using Roll20 as a player recently to cast fireball I needed to 1) click on the fireball action on my character sheet 2) minimize the character sheet window so I could see the "spell" window that had opened up UNDER the character sheet window 3) click on the spell window to cast the spell 4) go to the sidebar and put it in "chat" view so I could see the damage I rolled.
I have only used Foundry for about a half dozen game sessions so I can't give an in-depth review. It has a great UI but the lack of support for published materials is big drawback.
I have looked at Owlbear Rodeo, and it seems great as a bare bones VTT. Having invested time and money in the more complex platforms I don't see why I would ever use it myself, but I would recommend it to anyone new to VTTs who wanted a no-fuss way to get started.