I remember reading a couple of days ago where somebody said the ML55 was faster. I didn't rememeber this as being correct. I finally found the 2002 X5 brochure that has manufacturer's claims. They are: ML55 AMG -- 6.4 sec 0-60 time BMW X5 4.6 -- 6.2 sec 0-60 time
The 4.6 is 37 lbs lighter, and has 22 ft-lb less torque