Pure road tyres such as the Conti Road attack or Michelin Pilot road have profiles that allow faster turn in to corners. They have more rubber on the road due to the fact that they do not have big gaps between the blocks. They generally have softer compound rubber as well that does not last as long as block tyres of course.
Long tyre life is important for some and some riders prefer to not use the outer 2" of the tyre and are very happy when the Tourance last a long time. Many people can ride really fast on all sorts of tyres, but its mostly the rider that makes them fast so they can ride around or through the lack of grip that block tyres such as the Tourance have and get the long tyre life.
I would prefer to have more rubber on the road by using a road tyre such as the P/roads or R/Attack IF, thats IF, I was not going off road.
I find that Tourances let go when lent over and powering out of corners because I push them harder than they can cope with, this does not happen with road tyres. This is worse in the wet when the lack of rubber in contact with the road when lent over is a real slowdown. I can put my thumb between the blocks on a Tourance and when you consider that you only have a cigarette packet size of rubber in contact with the road, a thumbs width is about 1/3 of available grip lost.
Your call - Mileage or grip - Off road or road.