I agree that the M5 is better looking than the E63 S. The E63 S is good looking enough to me but not as much as the M5. The engine, AWD, acceleration performance, greater tuning potential and engine and exhaust noise sold me on the E63 S -- a wrenching decision after a lifetime of BMW ownership.Nice!
I was looking at a white E63 S with the carbon fiber exterior package that was on my local MB dealer's lot. It was a very sharp looking car. I still like the aesthetics (interior and exterior) of the F10 M5 better.
I agree the M5 lacks in the exhaust department but that was resolved by putting on Supersprint race mufflers and AMS catted downpipes (total cost was under $5K). I have a little more induction sound as well with same carbon fiber intakes similar to Gruppe M (cost $2K). What really sold me on the M5 was the looks, the DCT and how rev happy the engine still is even with turbos. I always tailor my cars to my individual tastes so some of the M5's shortcomings I have addressed (modified exhaust and I even did thicker anti-roll bars).
You can't go wrong with either car. The E63 S is a great car and is very appealling.
Mercedes of Massapequa, in my metro area, has two killer white 2014 E63 S cars in dealer stock -- one a wagon with B&O and one sedan. They have the blacked out stuff as I recall. They look sharp as hell. But I am not a white car guy so I ordered my 2015 E63 S sedan in Lunar Blue. Every E63 I see is black, white or silver. I wanted to look different.