Obviously this thread has a bunch of inconsistent posts. Some say a stock C63 will beat a stock M3 DCT in a straight line, while M3 owners with the DCT tranny claim to run neck and neck with a stock C63. I have shared my scenario and I just want to add this important fact. I previously owned and SMG equipped E46 M3, while I fully understand the technical difference between the SMG and DCT trannys the techniques in running these cars are the same. Paddle shift down to where the car is in the power band and hit the throttle.
Unfortunately when driving the C63 equipped with the 7GA it's not the same. If you are simply "rolling" at 50mph even in sport mode the car is in gear 7 (over drive) and upon "mashing the throttle" the car will only go into 3rd gear. This doesn't factor in the time wasted for the tranny to mechanically read the input from the throttle and downshift to 3rd gear. Again, the negatives of an automatic transmission. However, from a 50 mph roll you can place the C63 tranny in sport mode and manually downshift to 2nd gear. That way you will be able to launch the car close to 6K RPM and in the power band which would then shift at red-line into 3rd gear. This makes a significant difference when these cars runs and I believe it will explain the "inconsistency" in the stories from different owners.
Please take a look at this video below. You can hear the C63 is in low gear (let's be honest guys the M156 is much louder the S65) and clearly wins these runs.