Selecting power valve method Holley 4160

My answer is, whichever way your engine runs and responds best. Just experiment around with it. No one way will result in the best results for everything. Anyone who tells you that is an armchair tuner. I've actually DONE it. My truck runs best using idle vacuum. Vixen runs best using cruise vacuum. I've tried both ways on both vehicles. I think the reason the truck runs better using idle vacuum is because of its heavy weight.