Coug... Your comment about retained speed done sent me back to the ballistics program.

Retained speed, energy and momentum at 30 yards on the same arrows I used above:

LB 575 - 173 fps 38 ft lbs .4419 lb/secs

350 gn - 277 fps 60 ft lbs .4303 lb/secs

CP 575 - 206 fps 54 ft lbs .5244 lb/secs

350 gn - 329 fps 84 ft lbs .5109 lb/secs

The faster arrows ovbiously still carry more KE, the heavier arrows still carry more momentum. And the faster arrows have a lot flatter trajectory which is an advantage. How much of an advantage depends on the individual. The KE vs momentum argument has raged in the gunning community far longer than I' ve been alive, certainly longer than it has in the bowhunting community, and I know which ring I' ve thrown in my lot with. Elmer Keith was my guru as far as guns go.