I used XBMC/Kodi for about 10 years until I tried Plex about a year ago. Kodi's filesystem-centric view on media feels outdated in a world where almost all software is using intelligent search and filtering along with natively supported media info imports. This stuff is possible with Kodi too, but the plugin interface feels dated too. I also found it to be a resource hog on embedded devices.
But Plex has its flaws too. It swings the needle too far in the direction of Netflix-y for my liking, which is why I recently tried Jellyfin.
Jellyfin is a perfect medium between the two approaches in my experience of using it for a few months. I'd recommend any Kodi users who are wary of Plex to try it out.