RE: Heavy arrow, more KE....light arrow, more speed..??
I've used this arrow setup for 10 years: 29" Easton XX78 Super Slam 2314 with Thunderhead 125 broadheads. I don't know how much this arrow weighs, much less how much k/e I get. But, I do know this; I've gotten pass-throughs on 17 of my 19 kills. The two that didn't pass-through were poor shots.