Consistency of braking force is far better both overall and between the wheels. Always questioned how well the drums would do on a panic stop. Have seemed sluggish and have had lock-up. No such worry with disks as the controller is set just less than lock-up and is repeatable every time.
I had experienced some fade coming out of Death Valley with my drums. No fade with the disks and I rode them harder.
If you have ever driven an old car from the '60s with four wheel drums you know how much better disk is.