you're still converting the same amount of energy to heat, correct?
In other words, brakes made from the same material on the same wheel should experience equivalent wear if each one converts X Joules of kinetic energy to heat energy, no matter if they are applied on the front or back wheel?
I don't know.
Why do you expect that "wear" is directly proportional to "heat" or "energy dissipated"?
If I don't brake as hard, and therefore take longer to stop, is that the same amount of break wear?
A difference between the front and back may be that because the front is less likely to skid therefore you brake harder and stop more quickly. It's the same kinetic energy dissipated (more quickly) but I don't know whether it's the same wear.
Wear is clearly a complicated topic: Wear.
Here's one theoretical example of a non-linear relationship between energy and wear: if the braking is rapid then the heat doesn't have to dissipate, therefore the temperature increases, and therefore (if the brake's material softens at high temperatures) the wear increases.
I say 'theoretical' because sfaik bike brakes don't get hot enough to cause much brake pad 'fade' (in an extreme the heat is more likely to explode the tire if it's a rim brake, or boil the hydraulic fluid if it's a hydraulic disk brake).