I’ve got both Plex and Jellyfin running at the moment. Plex is nice for sharing with family since it’s more plug&play for sharing outside your LAN, and it is certainly a little more polished in some areas.
But I’ve been very impressed with Jellyfin as well, and would wholeheartedly recommend giving it a whirl. If FOSS appeals to you at all, it’s a solid choice.
In most cases, you really should have no issue running them simultaneously if you’re not ready to commit to a switch.
Seconding Plex / Plexamp if the use case involves streaming remotely. Probably the easiest to get up and running for remote access.
I’m not sure about the capabilities of hosting on a Pi, but it should be straightforward to run a couple different apps in parallel to test and compare features (I’m currently doing exactly that with Plex and Jellyfin)