Latigo gets my vote for the harder climb. Big John is right - after the first bit on Latigo there is no longer any cool ocean breeze. It seems to me that the 2nd half of Latigo after the middle flat portion is harder than GMR. GMR to me seems more of a consistent climb. Just be careful of the motorheads on Latigo - it doesn't get the traffic that Mulholland et al does, but it draws its share of motorized enthusiasts testing out their rides. Climbing either one, however, is an achievement.