if you are pulling a bob, or maybe even if you aren't, i'd suggest a mountain bike. the tire options for rough terrain are far better, as are rim options. 26" wheels, tires, and tubes tend to be more ubiquitous, but that might not help you much on the dalton highway or someplace similar. a low-ish end aluminum mountain bike is likely to have 3 water bottle mounts, rear rack mounts, and v-brakes -- all things you should be interested in for pulling serious weight on rough terrain.