Why would you take more of a chance riding a non Kevlar belted tire on gravel than a kevlar belted tire? I would think rolling resistance would be the least of your worries on crummier roads.
__________________
(Life is too short to play crappy guitars) 2006 Raleigh Cadent 3.0, 1977 Schwinn Volare, 2010 Windsor tourist. ( I didn't fall , I attacked the floor)