It's all about the speed and weight zrex. You add the speed and weight to push that super sharp broadhead through the animal. The more the weight of the object, the more retained energy at distance. The more initial speed, the more energy at distance. Put both together in the right spot on an animal, you have your pass through. Those that go super light on their arrows, to get that flatter trajectory, are sacrificing a bit, to a lot, of penetration due to the lack of weight to store the energy from the string of the bow. Those that argue that kinetic energy has no real value can't get that through their heads for some odd reason. It's a very easy concept but the speed freaks in today's archery world just can't seem to wrap their minds around it. To make my point with some of them, I pull out my little ole 75# recurve that pushes my cedar logs, that weigh an average of 630 grains with a 125 tip, at around 245fps. I then have them shoot their little super speedy 450gr total into a Mckenzie (the older solid ones) and I shoot mine into the same target. Both at 20 yards..I then tell them to go look at the penetration difference. While they are having to put both feet on the Mckenzie target and pull their guts out trying to get MY arrow out, I'm sitting back giggling and wondering if they get the point.