Switching between wasn't seamless, it kept forgetting where I left off on the last device, which was pretty annoying. Also, mobile/remote connectivity was spotty for me. Never got to the bottom of that, but my best guess is Plex's relay system makes up for a lot of random network issues. My best work-around was to add my phone to tailscale, but obviously that's not a great solution and won't work for a lot of devices.

Overall, my impression was that Plex is a lot more polished. I also bought a lifetime membership years ago, so I have no incentive to switch to something that isn't better. Plex isn't perfect, but it was still better than Jellyfin as of a few months ago. I honestly hope that changes soon, I have zero faith in Plex as a company.