physasst's point is a good one about road shoes generally being stiffer than MTB shoes. I don't think that's true at the higher end, but inexpensive road shoes are usually stiffer than inexpensive MTB shoes. If you have better-quality MTB shoes, though, the difference goes away. I ride Sidi Dominators and Egg Beaters, so I've got a very small pedal surface to work with, and even on 100+ mile rides, I don't experience hot spots, loss of power transfer, anything like that. And the Doms have been worth every penny. I used to buy a new pair of shoes just about every year, but have been riding these for 2+ years now, and expect them to last me at least a couple more.