Momentum vs KE
Incorrectly benchmarked in bowhunting, KE has absolutely no indication of penetration or for measuring the tissue destruction protentional of projectiles traveling less than 2500 fps. In fact, KE was never intended to be used to measure arrow penetration (read more here).
Momentum is a much better measurement of penetration potential than kinetic energy. See why below...
We provide this momentum vs kinetic energy calculator here so you can figure out the penetration power your set-up is generating.
What you can see here is that lighter, faster arrows may have a higher KE value than a slower moving heavier arrow - but they may have the exact same momentum value.
All momentum is not created equal. A slower moving heavier arrow will have a greater 'time of impulse' than a lighter faster arrow with the same momentum value. The slower heavier arrow will be able to push into an animal or into a bone longer than a lighter faster arrow with the same momentum value because inertia comes into play as well.