The pulleys are only really noticable on big cams when adjusted for power gains.

The main reason for Verniers is to get the cam timng bang on, after all most cosworth heads have had a good few skims so with a head that has been skimmed say 3 times, the belt is not going to line up exactly so the verniers allow to be "dialed in" to put the belt Spot On as without them on a head that has been skimmed loads, std pulleys can make the belt be out over a tooth which isnt good.