What you are saying has logic behind it, but the way KE is usually measured tends to negate some of the types of energy that are being mentioned as wasted or non-directional energy. The KE is determined by chronographing the arrow. When this is done, the forward motion of the arrow is measured in fps. The Chrono does not measure rotational energy, vibration or any of the other wasted energy. Energy can be wasted upon impact as well as on launch. I don't really disagree with the idea of momentum being more important, but I'm not convinced that KE is really so irrelevant. I also think broadhead style is very important. I generally use an old bag target to shoot broadheads into. I can shoot Muzzy practice blades or Slick Tricks into the bag, and it stops them every time. If I put a cutting nose Phantom on the arrow, it sails clean through the bag in buries about 10 " of shaft into the ground. I do know quite a few guys around here that shoot Rocket Sidewinders (1.5"cut) from 60# bows, shooting carbons, and blow through the deer pretty consistently. That would not be my first choice if I wanted good penetration, but it seems to work for them.