It's more than just "MJs have this, XJs have that" rules. By and large, XJs will have more amenities like power windows and full consoles. MJs were typically more bare-bones. MJs never had ABS, a lot of XJs will. MJs don't have a front prop valve. XJs rarely have shift-on-the-column. XJs will have a washer bottle that typically has a rear window pump. Lots of little things that can throw Jeepers for a loop if they aren't expecting it.