I think your question really is whether it is better to have the energy available as the result of more mass and less velocity as opposed to more velocity and less mass which of course is the concept of momentum. As I have explainded earlier, it is better to have the former condition. Like I've always said, with regard to penetration, heavier is always results in more penetration. The caviat to this is of course that the archer can not choose between momentum and ke, he can only choose a heavier arrow which of course will result in greater penetration potential, more KE and more momentum. To argue over which concept, KE or momentum, is more important is IMO not very usefull.
I understand that both KE and momentum are linked, and cannot be separated when considering penetration. However, they are not equal measurements and they change in a disproportionate manner depending on whether one is concentrating on speed or on a non-deflecting arrow path.
Let me rephrase my prior example. If I'm trying to get the least amount of deflection, should I concentrate on getting my 300 grain arrow that flys 300 fps, up to 325 fps (a 17% increase in KE), or should I try to increase to a 600 grain arrow that flys at 230 fps (also a 17% increase in K.E)? I do not believe penetration would be equal, yet the increase in KE would be equal. The arrow with the highest momemtum will penetrate furthest when hitting a mixed media, where deflection is likely.