I'll start. Did you know you can run a headless version of JD2 on a raspberry pi? It's not the greatest thing in the world, but sometimes its nice to throw a bunch of links in there and go to sleep.
I only watch on one device (Nvidia Shield Pro) directly and do not need streaming over the net. Because of this I have also not looked into Jellyfin much either.
Overall I got to know Kodi first and like the customization and add-ons etc. I have my library/metadata set up that way and am too lazy to check the others out and maybe switch (don't fix a running system, right? xD)