You can't compare the 2. Apples to oranges. Our M5 is a blast to drive. It handles very well but the power is the reason to buy the M. The X5 has more room but the M handles 4 people very easily with it getting tight fitting 3 in the rear seat. I find it doesn't do well in the space department. The trunk is large enough but the subs with the premium sound hang down pretty far thus limiting the carrying capacity. Repairs tend to be more frequent and can start adding up quickly. Choose your M5 wisely and be sure to have a ppi done. I would stay with an '02 or '03. The M5 in a word...intoxicating. Good Luck!