I’m probably not the best person to answer this, since I read almost nothing on furry sites anymore and post very little, but…
None of them are ideal, but feature-wise I do think FA ends up at the bottom. That said, I started out on FA and still post there for now because that’s where my readers still tend to be. I have a Weasyl account as a backup, and I like their folder system and how the stories display, but even though things have picked up a little, there’s still not a lot of traffic there, especially for writers. Inkbunny I had an account on when they got started, and liked them well enough, but their “no humans in adult works” policy, plus the reputation they gained shortly after, both turned me off. I avoided SF because of their reputation back when they were Yiffstar of being mostly an adult story site (and I never could stand the word yiff, let alone their “I came” feedback button). Thankfully things have changed there to some degree, and I would probably have an account on SF now, but at this point I don’t feel like it’s worth the time and trouble for me to set up yet another furry gallery when I’m tapering off participation on the furry galleries I’m already on, and trying to move my attention to things like my mailing list and my blog.
At this point, all I post to FA/Weasyl is reprints; I don’t get enough feedback anymore to make it worth posting original work that I could sell elsewhere first, and I admit I’ve gotten a little disillusioned that most of the audience I worked hard for years to build was (or is) apparently just there for the free stuff. (Well, that in itself wasn’t really a surprise, given that I follow tons of artists I’d never commission or buy prints from, but the percentage still disheartened me a bit.) I think a lot of my followers from the Thursday Prompt days have moved on, and since I don’t read and comment there nearly as much as I used to, I also don’t get nearly the faves and comments there on my own work that I used to get. Everything runs its course, I guess (and I guess that also goes back to what Ocean was saying in the other thread about not expecting followers to translate to sales)…
Ideally, I’d advise just cross-posting to several sites, but that’s far more difficult for writers than artists. As far as I know, there’s no single file format a writer can easily post to FA, Weasyl, and SF without having to alter the formatting in some way.