these are my opinions and experiences alone.
SSR lasts forever on the road but suck turds off road.
MT/R lasts forever on the road and does well off road.
Xterrain lasts forever on the road and does well off road.
the best rock tires are the krawler, IROK, TSL(sx)
with a FEW exceptions a good road tire is a bad off road tire and vice versa