the larger bore increases stopping force or reduces peddle effort. you can think about it like this. between 2 set ups peddle effort is the same so that's X psi in the bore and one set up has a 1 square inch piston and the other has a 2 square inch. the one square inch piston will exert X pounds on the pad and the 2 square inch piston will exert 2X pounds. basically psi times surface area = force.
