I have both and like both. I also have mechanical and hydraulic disc brakes.
Given the choice if I could only choose one bike? It would have rim brakes for the simplicity. If I was given the choice to have a second bike, I'd choose mechanical disc brakes. But, those Shimano XTR hydraulic brakes on my MTN bike are really something special. Powerful, feather/modulate well and can lock up the wheel on demand if I want to. In other words the best darn brakes I've ever had.