I owned 18' CP M4 and here is the good and bad things.
Good about it:
It looks much better for me I had individual color see picture
It was MT
Handling corners really good
Bad about it:
Traction issues when the temperature drops below 60F and specially when it rains.... you stop on busy street where you need to cross, boy you better wait
Good about M5:
M5 is just much more luxury more powerful and the best thing is AWD it can put the power down. It hides the weight pretty damn good, handles corners almost as good as M4
Bad about it:
Not as good looking and very expensive