Speaking from the engineering perspective, based on physics and fluid dynamics, yes it will slow the arrow down compared to a smooth blade broadhead of the same shape, size, and weight. How much? Not enough to matter! Friction, fluid drag and eddying, tissue impingment, it is a very long list of factors affecting the head drag in tissues friction coefficients. The differences in that small of an area are really minimal. If your shot is from a good angle the head will still penetrate all the way thru a deer size animal. On a bad angle shot, or a deer turning as it is hit and a hit in the paunch or guts, etc... then this could make more of a difference. Enough to keep you from making a kill instead of a lost deer? Perhaps.