Originally Posted by
FBinNY
If either fit, either is OK. Functionally they'll be very similar since the distance from the shoes to the pivot will be the same.
So the smaller brake will probably be lighter. OTOH (and this depends on the details of construction) using the larger brake at the top of the slot, vs the smaller one at the bottom, may give you a stiffer brake, or more leverage.
That's because makers engineer their brakes around their length. So to compensate for the loss in leverage with the longer brake arm, they increase the cable arm proportionately. They also might add more material to stiffen the arm.
So, it's still your call, but all things being equal the larger brake may give you better performance, though at the expense of more weight. Of course, the devil is in the details.
This.
I would assume that both these brakes will offer similar performance (leverage) if the pad is mounted in the centre of the slot. In general, if the pad is higher in the slot of a caliper brake the brakes are stronger. If the longer brakes will be set at the very top of the slot and the med reach brakes will be set at the very bottom, the long reach brakes will have a considerable advantage (all other things being equal).
Good quality cables and pads are as important as the type of brake.