It mostly comes down to personal preference honestly.

Jellyfin is open-source and more focused on your own selfhosted media. I, too, bought a Plex pass years ago and have enjoyed Plex but they've been adding a bunch of crap to their interface.

I'm big on free open-source software but I won't be biased and say that Jellyfin has some rough edges, but it works well enough for me to watch movies with my wife. Plex is a bit smoother and more production-ready for those power users that host Plex for several others.

I'd encourage you to try it out if for nothing more than exposing yourself to alternatives.