Road hubs have an OLD (over locknut distance, or spacing between dropouts) of 130mm, and Mtb hubs have an OLD of 135mm. Consequently MTB hubs generally have more hub-center-to-driveside flange distance than road hubs, which results in less wheel dish with MTB hubs. This generally means greater wheel longevity because you can build wheel with more tension on the normally-lower-tensioned non-driveside spokes. If your bike's rear dropouts have 135mm OLD (spacing) then you should definitely use MTB hubs for your wheelbuild (or MTB wheels).