Because you can give your friends a login, they can log in from anywhere, and watch your content. Same for you. You can log in from anywhere and do that. Kodi is more of a local thing, I find the two compliment each other very well. There are native apps for jellyfin as well. Loaded up and hit play. I guess you can probably do this with Kodi but it hasn't been designed from the ground up for this use case.

The most useful part of Jellyfin is on-the fly transcoding to whatever bit rate I want at any particular time, no matter where I might be. I've watched stuff off my server on a train with terrible connectivity by setting it to 360p. If you only watch at home, then it's probably not that useful to you. I also like all the library features and tracking my per episode watch history for shows.

Same here. I never could figure out why I'd want to use anything else. Plex, Jellyfin, Emby, whatever. Nothing beats the simplicity of a couple of terrabytes on a local drive, or if you want to get fancy, a NFS share.

Honestly, Kodi is even a little more heavyweight than I need, but I've been using it since long before the XBMC->Kodi name change and have been happy with it.

Thats a good idea for a damaged laptop, I often see those for sale for nothing