[Dave at Pelican Parts]

The 911 brakes are better, generally speaking. You shouldn't notice much difference in a single stop (frankly, the tires are likely the dominant factor there), but the 911 ones will hold up to heavy use/abuse much better. They have vented rotors, which will take away a lot of the heat a lot better than solid rotors can.

The extra fluid capacity and pad size will also help absorb more heat before the brakes start to lose their effectiveness.

--DD