I think both have positives & negatives when it comes to trying to figure out how much penetration we will get. I think a good general rule from my experience has been that arrows that fall within the 400-450 grain range seem to perform better. They are not the fastest nor are they the slowest. just a great mixture of speed & weight. I will say this though - a 2315 with a 125 grain head is a lethal combo out of any bow that it spines correct for!

From my experience I also have noticed that with any given shaft a heavier tip like a 125 grain tip really seems to penetrate a lot better than a 100 grain tip. with all else being equal the amount of speed given up isn' t very much at all but that heavier tip just seems to really hit much harder.

which is more important? heck who really knows! They both have merit & should be considered.