The RC51, The previous unit's brakes were fine, but the new four-piston jobbies are even better. The old brakes were extremely progressive--once activated you only had to move your finger a smidge to stop the bike. The new brakes are totally linear and require more lever travel, providing better feel, easier modulation and more feedback.
The RC51 is very light compared to the Busa and has very aggressive brakes. You can't compare the braking of the Honda to a Busa, anymore than you could compare the top speed of a Busa to a Honda! Cache is right got to get use to giving the front brake alittle more squeeze than the smaller liter counterparts. Not to hard or you'll be riding a STOPPIE!