I run both similarity on the same box with the same source library but still prefer Plex for many reasons. One is that the nicer findroid app doesn’t seem to support Chromecast, which is how I watch all media 99% of the time. Also the JF UI is a bit rough between laggy menu interactions and views sometimes having transparent backgrounds causing you to see the previous view underneath while transitioning between screens. I also don’t like that the continue watching in the default UI uses landscape cards for each title that take up way too much space, and neither the default app or findroid has a recommended tab for individual library folders (like how in Plex I can go to movies and see recently released, added, top in genre x, top by director y). I think that would really draw me to use JF more. As it is it feels like I just have to resort to browsing the alphabetical list which I hate doing with thousands of library items.