Think old school 4x4 with locking hubs.
You can put the TC in 4 hi or low, but unless you lock the hubs only the back wheels will actually apply power to the ground. Also, you have to lock both hubs or the axle with the hub unlocked will get all the power (unless you have a diff locker...
Since the JK front axle doesn't have unlocking hubs, both axles are always turning and the front diff is always doing it's thing allowing the axles to turn at different speeds.
It sounds like JL has 1 unlocking axle, so only one axle will be turning and the diff will just free spin.
If you're thinking about a well optioned 4R, look at the Lexus GX 460. It's worth it for the V8, IMO.
IMO, Toyota's do last longer, but when they do break things tend to be more complicated and expensive to fix because of some weird design choices. Starters under intake manifolds, comes to mind.