I agree 100% with ya Yoda, but I see a ton of guys that don't get there wheels for free on carbon rims in the B and C races. I am just not into it.

the big thing is the wheel depth. I agree braking is likely/ really affected and the grit from mud& sand will reduce the lifespan of the brake track, but in deep sand and mud the deep section wheels will cut through better than a standard 25-30mm depth wheel. The reason is that in the shallower wheel the mud/ sand can wrap around the rim and actually impede it from moving. Think about getting your rubber boot stuck in a mud puddle, the sand or mud will make the difference, it is not for aerodynamics but for mud dynamics. So because there are not that many alloy deep section wheels most/all will be carbon.