I drove both and decided on the CLK550. This one came with Renntech chip, custom rims and performed much better than 335is I drove. I felt this would just simply run circles around the BMW.
How do you run circles around a 335i with a car that's a crappy drive? All this tuned thing might do is be faster in some straight line sprint. For the rest the 335i is superior in every possible way, not to mention it's easy to tune and easy to be made MUCH faster than the CLK.
Being the owner of a slightly modded 335i E90, i'd choose CLK. V8 is V8. A friend of mine had a CLK with V6. Such a pleasant car. CLK has only 2 doors and was too expensive, but if the money is not an issue...
It's just the old half arsed medium Mercedes Benz. It's design is a very sluggish/Banana uninspiring one. It also drives like an old Mercedes Benz and last but not least it had the bad luck to be part of a generation that had stellar members like the SL, CL and S of the time.