As I stated, I ride on gravel roads, and if it's wet at all my rims are constantly coated with sandy mud, and it grinds rims down quickly. No problem with the discs.

Rims work pretty well most of the time, and I think they may be better off in cities where you're using them more. However, on my ride I often go 30 minutes without touching the brakes, and in freezing rain that means that the rims get coated with ice.