Please say Why?
(NOTE: None of these cars is an AMG or M series - just standard).
NOTE: I am talking about the MERCEDES CL (only) and that is different from the Mercedes CLK and the Mercedes CLS.

The 6-series. It's sportier, better-looking, and I love the '80s 6-series.

But this isn't a very fair comparison. A 650i costs $75,000, and a CLK550 costs "just" $55,000