Not to overburden this thread, but the CLK six cylinder may be a nicer ride in the Wash D.C, area. It will probably run cooler in the heat of the summer, and it has the same top speed as the CLK500- computer limited to 130mph.
I am not sure about weight, but if the six cylinder is lighter in the front, it may handle nicer than the eight cylinder.

Remember that traction control makes a difference in the snow.