jellyfin has some nice features that will probably never come to plex, but in the end plex is just so much more pleasant to use. i have both setup against same library and in practice all i barely use jellyfin except for some minor use cases
And how does this scale? As more of those feature come, and you cannot opt-out of them, even as a paying customer.
Plex has a horrible report with me, and though I still use it, I'm tempted to try other apps now.
Maybe our use cases are different but there's nothing reactive needed for me.
I just checked to see if I put my finger on the rough edges and the biggest one is around navigating through the library. While both Plex and Jellyfin can sometimes fail to find the "best" cover art, Jellyfin misses about 8-10x as often, often yielding random screenshots from the movie or a crazy zoomed-in view of some cover art. Plex far less often misses. (This is running the latest on both and giving both a full metadata refresh of the affected libraries and then the affected title again just to be sure: Jellyfin 10.8.10 and Plex 1.32.3.7192.)
What did you find JellyFin had, that Plex didn't?
That's a huge plus, however sadly Jellyfin doesn't handle subtitles well, and I really dislike the lack of a quick "skip forward" action. So I tend to still use Plex.
An Open source License