I used to use Fantasy Grounds (right from it's very first inception), but I don't any more. Three years ago, I switched from a PC desktop to a Mac desktop. To get FG on Mac OSX you have to go through Steam. And I'm wary of Steam (for a bunch of reasons I don't want to go into here). So, I switched to Roll20 (where I've been for 2.5 years). Yes, Fantasy Grounds was "prettier", but I find Roll20 more "practical". I'm a "make it myself" person anyway, so pre-fab mods don't lure me. The only downside to Roll20 is they still have bugs in the Audio+Video side of things (but I use Roll20 through Skype or Google Hangouts and the probs all go away). So, in summary: Roll20 is my pick of the two (for very personal reasons).