Disc brakes are not all about power. The main advantage disc brakes have over rim brakes is improved modulation. Rim brake modulation can be improved upon, and inversely disc brake modulation can be ruined, depending on component choices, but in general disc brakes have the better starting platform. The ability to hold the rear brake at the threshold of lock-up and finesse changes with low lever effort is equally important on the rear as at the front of the bike. Good rear brake modulation is extra beneficial on a single user bike in instances where the road tilts downward and the rear goes light.