There’s definitively more to a distro than the shell prompt and wallpaper.
Besides the obvious package repos and how well package interoperability is maintained, there’s also differences for default configuration. OpenSUSE offers sane options for security OOtB, IMO.
Then there’s also linux itself. Some distros build the default kernel package with a set of patches to improve typical usability, while others just ship an untouched upstream version. Some offer alternatives while others don’t.