Mostly on BIG hills. If you live in flat land and run stock tires you'll never notice a difference.
If your brakes are fading, you're not using them correctly.
If I can descend Mt. Evans with no brake fade, you can descend
anything, given correct technique.
Captain Ledd, your parts guy got the shoes switched. The 10 inch brakes are ENORMOUS in every dimension compared to 9 inch.
But too much braking power means you lock up the rears and spin out. That's what RABS is for, but no competent engineer wants to engineer an RABS failure mode that kills the occupants. This means you'll have to
compensate away the difference, in proportioning.
I find that my Exploder with its 10 inch brakes stops about the same as my former Bronco II with its 9 inch brakes. Which isn't surprising given that they have the same
front brakes.
It's amazing how many RABS RBVs have nonfunctional rear brakes. If you're having a problem, make sure your rear brakes actually work. Or they won't work after a swap, either.