the way i see it is a bow thats rated at say 315fps IBO if i can shoot a 550 grain arrow and still be around 230fps (example...only guessing) im gonna go with the heavier arrow....people act like 220 is slow when it is not by any means.
And just think, you could actually get to the "bone breaking" threshold of 650 grains and still be shooting over 200 fps. At hunting ranges, this will cause no problem with trajectory, and your arrow becomes that much more deadly.