Smoother modulation?
Option to run lighter/more aerodynamic rims?
Rims last longer?
Avoid brake dirt?
You could also add improved braking performance in the wet. I think disc brakes will transfer over from MTBs to road bikes in the not too distant future.
You could also add improved braking performance in the wet. I think disc brakes will transfer over from MTBs to road bikes in the not too distant future.