Would go with neither of these, and look at a hybrid, takes the best of road and MTB's and ends up with a good compromise.

The problem with using a current road or MTB is if you are looking to add a rack, unless you are looking at a low end model, they don't come with the required mounts anymore. Hybrids are easier to get with discs, as the normally use flat bars, as opposed to drops where disc are still a few years a way from being common.