Since Kinetic Energy is determined by the formulaMass x Velocity = Force or kinetic energy what is the difference? I mean I understand shooting fast, light arrows for 3D but those same arrows produce almost = amounts of KEwhen compared toheavyier, slower arrows. Now consider the fact that it takes about 25-30 of kinetic energy to pass through a whitetail, unless you are dicussing hunting heavieranimals with thicker skins and bigger bones or you are a child/women or in some other way limited in your draw weight kinetic energy is important only if you are worried about how far your arrow sticks in the dirt after it passes through the deer you shot.

For example some numbers::
330 grains at 310 fps=70.44 ft lbs. of ke
450 grains at 270 fps = 72.86 ft lbs. of ke

I'm not seeing the difference as being very significant, both are close and well above what you would need to kill a whitetail.

Here is a KE calculator from Easton:
Bowhunting Info Kinetic Energy Calculator

And another with an article I found interesting:
Arrow Penetration - much ado about nothing?