Piston area is only important if you have trouble achieving the point of lockup.
There is no need to press the brakes harder than locking wheels
Just press the pedal a bit harder if there's a little bit less piston area.. Lots of racecars have really hard brake pedals (little brake boost) and need a firm drive.
The real braking performance, that is the stamina, is dictated by pads and disks (it's all about heat management). For large pads they use mulitple pistons to achieve a pad pressure that is as evenly as possible.