I've got both cars. 2004 Crossfire 6 speed and 2005 SLK 350 with 7G autostick with standard suspension. Once broken in a bit, like Bullseye said, acceleration will be a bit better from the Merc. It is a tight engine at the outset and needs some run in time. A basic point to remember, the Merc is a hard top convertible and I suspect has a bit of a weight disadvantage to the Crossfire. On the otherhand, the Merc is 268 horsepower to the Crossfire's stock 215 rating. I cant drive both cars at once for a direct comparison, but the Merc is faster at the end of an on-ramp that I use for fun. I shift gears by hand, and I do make sure it is in 1st at the start, otherwise too much ramp up time is spent in second. Without a doubt it handles better than the Crosfire. The new standard suspension is great and the staggered tire sizes really help. I have heard that the Merc's sport suspension option is a bit harsher in ride, but handles even better than the standard package. You get what you pay for. The Crossfire is a great ride. The Merc is automotive engineering pushed to an extreme. Chipping the Crossfire is not going to make up the horse power difference. It might optimize shift points, but the 7G is a lot different trans than the auto Crossfire has, so you would still be at a loss in timing. I enjoy both cars. Kusheen, this is the reason I did not go after the Lotus in La Jolla. Got enough toys at present.
Rgds to all.
Chris