Not sure about US models, but none of the E430 4-matic cars sold here have limited slip differentials (GM called it "Posi-traction"). They use the ASR/ESP system to allocate traction to the tire that has some. All of the E430 4-matic cars had ESP/ASR standard.
Because of this, the current 4-matic system works best in on-road conditions. Since most ML's, and all C/E/S cars are road only vehicles, it's the best system.
The one drawback can be that it is hard on rear brakes in very poor conditions.
1998 C230 "Black Betty"