If certain brake pads say they generate less heat – and perform as well – then where does the energy go if not to heat?

A very good question 🙂

I’m assuming what they mean is that certain brake pads are better at conducting heat away from the contact surface and thus remain cooler, but that as you’ve realized isn’t the same thing.

Obviously Hope pads run cooler by converting the kinetic energy to sound energy.

I suspect what they actually mean is that they develop less of a temperature rise, which is not the same thing as generate less heat as strictly speaking all the kinetic energy will eventually end up as heat.

As above, depending on the thermal properties of the pad, and the thermal path to other bits, the pads could be cooler, but the same heat is being generated (for the same amount of stopping).

I suspect carbon rims prefer thermally conductive pads to help take heat away from the braking surfaces.

Higher specific heat capacity?

Better conduction away from the face?

Latent heat through sublimation?

From experience with some of the pads i have used, the energy is converted directly into sound! 😉