I have played online since 2013. I have many hours in roll20, fantasy grounds and Foundry.
Currently I know use fantasy grounds and Foundry. Roll20 I would never use anymore. It's too outdated.
Foundry is nice but it's just a prettier roll20.
Nothing compares to fantasy grounds. Nothing is as easy to use and simple. It's incredibly easy to run right off the bat. It's like going through a story book clicking pages and automatically setting encounters . The combat tracker is the best hands down. Even for my in person games I always use the fantasy grounds combat tracker. If you want I can demo you fantasy grounds.
I play 5e, CoC, C&C, SF2, PF2 and Aliens on fantasy grounds.
I play 5e, Aliens, PF2 and SF2 on foundry.
If you play 5e, PF2 or Aliens nothing compares to the build in character builders on fantasy grounds. You have to pay for foundry ones that aren't as good.