I actually sent that mail off a little too early. :) So, this is part 2.

Yes, the angular momentum  of the larger disc rotors does make the
brakes work less hard to accomplish the same stopping power.

My main point of my original message however wasn't that you would
notice much improvement on the brakes with a standard load, but rather
the upgrade should allow for better stopping with an increased load.

Since I haul around a trailer from time to time, the Big Brake kit
should allow for increased load safety. Noting that trailer loads are a
combination of issues. The HP of the engine allows for acceleration of
the load. The bigger brakes allow for decelleration of same. There are
still the tongue weight issues to contend with.