For enhanced safety, the front and rear seat shoulder belts of the Mercedes G-Class have pretensioners to tighten the seatbelts and eliminate dangerous slack in the event of a collision and force limiters to limit the pressure the belts will exert on the passengers. The BMW X5 doesn’t offer pretensioners for the rear seat belts. The G 550’s standard 4.0 turbo V8 produces 81 more horsepower (416 vs. 335) and 120 lbs.-ft. more torque (450 vs. 330) than the X5 xDrive40i’s standard 3.0 turbo 6 cyl. The AMG G 63’s standard 4.0 turbo V8 produces 121 more horsepower (577 vs. 456) and 148 lbs.-ft. more torque (627 vs. 479) than the X5 xDrive50i’s standard 4.4 turbo V8.