The brake caliper will have the same amount of power, only, the amount of leverage will increase. it will remove strain from the brake caliper and lever because less braking force will be required to oppose the same amount of momentum of the wheel. The frame and fork mounting locations must be...
its really easy to break torque on a rusty bolt if you have a good grip on the fastener, and a sufficiently long breaker bar or wrench. You would find this difficult with a good grip and a short wrench.
The thing about bigger rotors is that you are moving the caliper further from the center of the wheel, this creates more Torque, or leverage to the turning wheel which results in less effort required to slow the same mass down at the same speed, or the ability to stop faster.
Torque = Force...