Interesting Jeep thread over there....
QDII...mechanical?? Well, QDII is more of a hydraulic system (fluid pressure based on wheel speed differences). Aren't the differentials made of clutch-packs?? Yes. Clutch-packs are weak and wear considerably with off-road use. Check out aftermarket differentials...the most popular ones are gear-based. To be durable and reliable, you need gear-based mechanical differentials, like the 4runner's center diff. My old Honda CR-V uses clutch-packs on the rear differential?? It's 4wd system was based on hydraulics too! Same story, different character.
Hmm, so you gotta ask one question...do you want to replace brake pads (4runner's ATRAC) or differentials (Jeep's QDII)??? I know my choice.
Unibody?? Yeah, it's great to have in a car, but in an off-roader???? Unibody's don't stand up to off-road abuse well. They are also very costly to repair...and once damaged, unibodies are never the same (in terms of strength).
The ONLY true Jeep is the Wrangler. BTW, have you seen Jeep GC's crash test results?? Let's just say that the Wrangler is the best crash-testing car Jeep has to offer!!

It's true...go check it out.
As stated above in the link, the Jeep's QDII system has a bypass valve that prevents full locking of the differential. Therefore, in extreme cross-axle situation, QDII is no better than an open diff!!
I love how the JU people criticize Toyota for cost-cutting! Who are they kidding??!! That's just sad.