I switched to jellyfin about 6 months ago and I can say it is definitely worse. I’m constantly fighting to fix thumbnails, fix episodes to be in the same show, force rescans to get it to even recognize a show that already exists. I never had any of these problems with plex.
Plex also defaults to transcoding which fixes a lot of gaps with clients that don’t support certain codecs. I’m often running into issues where infuse can’t play DTS so I need to reencode before I can play the movies.
Also in the process of ditching plex I switched to audiobookshelf for my audiobooks and I have to say it’s also crap. It’s constantly refusing to start playing, or pausing for a really long time before playing.
All that being said I’m not switching back. It’s been a pain but it was worth it.