Imo the only other time for big rotors is long descents that are steep or tech which require a lot of braking. After a while most people hands cramp up. Most newbies come to whistler (or any resort) with some dh experience. Within 4 hours their hands are paralyzed with pain. 10 runs and you have decended approx 33,000vert ft. 8 inches helps reduce a lot of that pain.

Past that and weight 6's are fine.