Road bike for sure! If you are already riding a mtb on the road, you are already using it as a hybrid. Now you need a bike that is even lighter and faster for longer distances! There's just not enough difference in a mtb and a hybrid (imo) to justify buying one of each. You could always put 1.5" slick tires on your mtb, and there's your hybrid. If you want something that will really make a difference, go for the roadie!