It's not so much a question of one vs another. It was asked the most cost effective way to accomplish such.

Last I knew Plex required an ongoing subscription for some aspects that Jelly has for free, so that consideration is part of cost effectiveness.

Personally I have Emby simply out of inertia since I bought a lifetime licence before there was a Jellyfin spun off, but didn't propose that because it would be an unneeded cost.