Another thing to add about brake rotor size is this. What a brake actually does is turn the energy from the forward momentum into heat energy. Remember, that the energy has to go somewhere. Brakes, however, can only work effectively up to a certain temperature, after that they fade. A larger rotor can dissipate more heat. It has more surface area and one point on the rotor is in the cooling phase longer. You can have all of the clamping power in the world, but if the pads overheat, the brakes will do very little.
As far a balance on a bike goes, scientists still argue that subject.