In hill country with long descents, rim brakes come up short. That has been my experience but no one believed me, so I recently did calculations; Circumferential force at the rim pads on 406 was 44% higher than on 622 (700c), which means requiring higher contact pressure, so greater heat, while 6% less rim travel at the pads. That, coupled with the 35% smaller rim so less heat sink, means higher rim temperatures on long descents. Steel rotors and pads can handle higher heat than aluminum and rim pads; The aluminum doesn't melt, but it does expand and pull harder on the spokes.