The only valid comparison would be the CLK320 vs 330Ci. I did not try the covertable models but I did test both coupes (CLK320 and 330Ci). The MB is larger and much more refined, both in terms of interior and engine. The BMW engine needed to be driven harder to get the most out of it the MB had much better low end torque. The interior noise is higher in the BMW. Road handling the BMW330 is slightly ahead of the CLK320 also the steering is more direct so the overall driving experiance is closer to the road with BMW.<p>As far as abosolute performance is conerned the CLK430 is way ahead, you simply cannot beat the big V8!. However, for me the difference in performance between the 320 and the 430 was not worth the extra $. The 320 has enough power for almost all drivers and will outperform most cars on the road.<p>Finall the BMW interior is some clunky compared with the MB and the MB rear accomodation is a little more spacious.<p>Both are nice cars and most people would enjoy either!