Just between you and me and the fencepost, speed with light arrows is what's selling bows, it's what's popular now, and KE correlates better with speed than momentum does. Many people don't at all care to be reminded that guys shooting longbows with wood arrows and cut on impact heads are zipping thru elk and moose with only 40 ft lbs of energy, but with arrows weighing between 10-13 grains per pound of draw weight and carrying high momentum. Why not? Because it doesn't fit neatly into their rationale for shooting very light arrows at 5-6 grains per pound, as fast as they can, at animals.

But watch the forums over the next few weeks. We'll start seeing many variations on the question, 'why didn't my arrow get good penetration?' and I'll still be hanging around saying 'try a heavier arrow.'

I still say that arrows in the 7-8 grains per pound range will give better penetration than lighter ones, regardless of what material they're made out of, without sacrificing all that that much in speed or trajectory. A little less speed for a little more energy and a good bit more momentum. It's a good compromise, IMO.