have never driven an m3, but had an e60 m5 and now i have a 2012 cls63, and i can tell you if its handling and driving experience youre into, forget the cls63
even the e60 m5 handles WAY better.
CLS is a boat. and feels as heavy as a tank when you drive it.
no agility, and really makes its size known.
mushy throttle response too.
ive only had it a week or so and im bored with it already.
really wish id have test drove one first, but they dont allow test drives on these types of cars where i live.