BIG front disks (13"+)

Assume that you are applying the same force (A) to the rotor via the pads and the coefficient of friction (B) is the same (Frictional Force = A x B or rather FF= AB). Yes you will be applying that force at a larger distance from the hub (torque= FF x distance from hub or rather T=Fd) but lets consider angular momentum (Angular Momentum = mass x velocity x distance from axis of rotation) into this...the further from the axis of rotation the faster it is moving hence you will have more momentum to overcome. This is especially true when you consider that larger discs have a larger mass as well.

What a bigger disc will do it prevent the brakes from fading during prolonged braking....due to increased heat dissipation.