Wow! Glad I actually had hunting to do this weekend to try and add to my measlie 24 years. You can put me in the middle-of-the-road crowd on this one. There's no doubt that a heavier arrow out penetrates a light one given equal energy behind them. And, I don't think that anyone will argue that in most instances a lighter, faster arrow may be adequate on easily to moderatly tough to penetrate game (anything in North America with the possible exception of bison and mt. goats). My stance is to shoot the heaviest arrow that I can get moderately flat tragectory out of with the best accuracy. For my set-up that just happens to be a 500 grain arrow at 265 fps. It's not a log and it's not a scream machine but it does hit exactly where I point it and I have utter confidence that it's going through whatever I hit when it gets there, and that's what matters.