[BarneySlayer]

Kinetic energy is directly proportional to the mass of the object and to the square of its velocity: K.E. = 1/2 m v2

It would seem that for hunting, more velocity would be better.

That seems rational. However, if you look at the root of it, if your goal is kinetic energy, the best indicator of that is kinetic energy.

Take that further and realize that the energy that goes into additional velocity has to come from somewhere, and it takes an exponential amount of energy to increase velocity. What goes out cannot exceed what goes in.

That's why car collisions at 25 mph are serious but not usually life threatening, car crashes at 50 mph, if they involve an object that is solid, like a concrete barrier, are pretty damn nasty, and at 100 mph, there's not much left.

But it comes to address the point, when people think they're getting more energy by lightening the arrows to gain speed, unless they luck into some marginal change because their modification improved the tune and therefore the efficiency of energy transfer, they typically see a loss in efficiency, and total energy, because the faster the arrow moves, the faster the moving parts on the bow move, and that means that energy put into the moving parts of the bow that don't even begin to stop until the arrow is no longer being accellerated (to pull off the string, the string has to 'pull back' that doesn't get transferred to the arrow. So faster arrow is, as a matter of general physics, less efficient.

Of course, it's hard to hit much lobbing rebar, so you find a general compromise that still has enough energy but flies well enough.