I plan on only using Derpi to save/transfer images to my computer or other sites. The mods are being unprofessional and I think its collapse is only a matter of time. I'm not going to say soon, but when Derpibooru ends, it will be a fiery death.
I have hopes for Ponybooru, but I've seen Zizzy mention finding a "balance" with artists, and that worries me.
There already was a balance. They'd take down paywall shit and artists could have the exclusive right to upload their new content for three months. Seems completely fair. But if they want to play good guy, I wouldn't mind that as we get a functioning true archive.
Rainbooru ranges from broken to slow. But Raindev has more to work on since he isn't using Philomena so I can't complain. I hope it works out.
I don't know anything about Twibooru.
I like Ponerpics so far. The DNP is still in the works, and a hope it leans towards archival. I like Philomena so it'd be nice if either Ponybooru or Ponerpics could be an archive.
Furbooru went full censorship. No nazis. No foalcon. Nothing "hateful." No "antagonization." I guess mods will decide what that means. I don't plan to speak much there because criticism or humor = antagonization with these people. I do like that it's not just pony content though. I like having strictly pony boorus but it's cool to have a Philomena e621. Just wish the mods weren't fags.