I still say the M4 off a GSXR with the baffle removed is the loudest. Can't hear headphones etc. Its TOO loud. I rode with a sprint that had the aftermarket 3 tip pipe (cant remember the name) leading, Duc S4RS with remus, and a harley with long shots. I was in the back cause of the pipe. When we stopped for gas the sprint asked how his new exhaust sounded. Both the bikes said "I dunno, couldn't hear it over the Speed in the back.." I couldn't tell you what any of them sounded like either. Hell I had a buddy that rides driving a car in front of me going to a party. He said the damn car was vibrating when I passed him, and they had the music up all the way when I was behind em. It might as well just be open after the header. With the baffle its not too bad, but still loud. Probably the same as comp werks.
EDIT: By the way, I have a decent tune for the comp werks and M4 GP that DoctorSpeedy sent to me if anyone wants it. Arrow low tweaked on a dyno. Its a tiny bit leaner than the standard arrow low tune I had on before. Guess even with the short open pipes the arrow low is too rich since its tuned for a new header. Runs much smoother, mpg is much better also.