I like Roll20 as a player. It has been a lifeline when I'm stuck working weeks or months abroad and dealing with the constant self-quarantine requirements from international travel. They have an excellent find-a-game function. But it just didn't work for me as a DM. I found it too fiddly. Also, I found that the large Rappan Athuk dungeon section maps, with walls fully traced, etc., would just lag and hang. Lastly, Roll20 just didn't provide enough storage at an affordable prices for the over 100 full-color maps I need for Rappan Athuk. Even with manual reveal, trying to put up a map on the fly was just not as convenient as Fantasy Grounds, Table Tools, or Foundry, where I can have all my maps preloaded and searchable within the VTT itself.
Foundry has provided the best prep experience in terms of line of sight, lighting, local ambient sound, etc.
The issues with Foundry are:
(1) Poor support for D&D 5e. For 5e you can't get all the official content, so you have to manually enter it or use a plugin to import from D&D Beyond. Getting the character sheets, items, etc. to work with automations, etc. is wonky. We use D&D Beyond for the character sheets, even though I can import them to Foundry with a plug in. Managing character sheets in Foundry just isn't competitive to Fantasy Grounds or Roll20.
(2) Mods can be too much of a good thing. One of the great aspects of Foundry is the community mods. You can add to the base programs functionality in some very cool ways. But it also means things breaking when a new version of the base program is released or a great mod by is no longer supported by the person who created it. Also mods can conflict with each other. If you love tweaking and don't mind the time it take to test and troubleshoot, you'll love it. But if you are more of the type that just wants to buy a game and play it, Foundry is not there yet.