Is the Plex on Android on Nexus Player experience better than the Plex on Android on Amazon Fire TV experience? I'm very unhappy with my Amazon Fire TV (which only exists for Plex purposes).
Yes. Plex's Android TV app is very slick. I was impressed.
Plex on AndroidTV is a different interface than the version that exists on FireTV. It's more polished than the FireTV version, but the recent additions to all the plex apps around recommendations really annoy me. I don't want Plex to try to be Netflix, I want it to show me unwatched videos in one section and all videos in another section, and that's basically it. Plex on iOS does the same thing, though, so my guess is that Plex on the apple TV won't be better.
It's already on the Roku, and I'm very happy with it.
Plex runs great on iOS devices, so this is probably a low-hanging fruit (to port).
I did try out the Plex app that runs on the Amazon Fire box (Android), but it was slow and didn't feel very nice. Not sure if that's because it's a different, less-optimized codebase, or the Fire is just underpowered.