It‘s been mostly rock solid. Kodi is more flexible in terms of interface. If you don‘t like plex‘s ui - tough luck.
I‘ve actually started using Plex for my highest-end Dolby Vision MKV‘s because Kodi didn‘t support playback yet. Might be different now.
Other than that I don‘t see massive differences tbh. Plex is certainly more of a „set it an forget it“ solution. Kodi is certainly a very good option, but if you have more than 1 user you might need some media server setup in addition (emby server, er even server side plex).
Edit: just updated on my shield. Does anyone know if Dolby Vision is supported now? Quickly tested it with a compatible movie - didn‘t work.
Edit 2: just looked it up. Apparently dual layer mkv is not supported yet. Guess I‘ll keep using Plex for this use case for now.
Kodi 19/Matrix broke that, however, so now we're just streaming directly from the NAS until it's resolved on Emby's end.
While the 2 experiences are nearly identical, we like the per-user/other device stuff that Emby brings in. (As well as outside-the-home streaming when we travel.) If you don't need or care about that stuff, just pulling from a central data store works very nicely in stand-alone Kodi.
The Emby and Plex apps are trash compared to Kodi if you care about flexibility/customization.
I have always been reluctant to go that path, it felt to complex for my home use case. I generally use ftp instead for this reason, but I guess it's not as efficient.
Kerberos would be far too complex to be warranted here - all that's needed is nfs-kernel-server and /etc/exports on the server side.
Granted, my network is reasonably locked-down (MAC address filtering, (reserved) IP addresses available matching the number of devices on the network), but security beyond that has never really crossed my mind.
EDIT: another common use-case for me is basically grabbing lots of youtube videos/playlists via youtube-dl, which then lets me watch them on anything and everything than can run kodi commercial-free without jumping through hoops (i.e. browser addons or sideloading third party youtube apps, etc)
For some systems they come as simple apps you can just fire up, or you can have the separate apps load up. Not hard to switch between them.