One minor technical difference: you don't need to actually flash a new OS to your device to remove Android bloatware, "/system/app mover" will do the trick. Of course this does not help if the manufacturer replaced core stock Android software with their own (Samsung), but at least in the case of Samsung I can't really complain on their replacements.
One example would be the "Orange Wednesday" cinema ticket software. I wasn't an Orange customer, I have alternative cinema ticket arrangements, etc. Just having to have that software on the phone was annoying.