Why are the 11.75 Brake Better?

What it amounts to is the "swept area" of the rotor- the amount of area covered by the pad in 1 revolution of the rotor. The amount of area covered by the pad in one revolution of a 10.85 rotor is significantly less than the area covered by the same size pad on a 11.75 rotor. Pardon me for not doing the exact math on it, but you get the idea.
More swept area = better braking. If it takes X amount of force to stop a car of a given weight in a given distance, that amount of force can be generated easier and quicker with a larger diameter rotor, with all other factors being equal. And since braking is a conversion of dynamic energy into heat (through friction), that heat is also more readily dissipated over a larger area when using a larger rotor.