If you have an adjustable weight system for your arrow, a chrono, and a calculator you could probably chart your own KE & momentum values for your individual bow. And then you can find out where they are optimized. Time consuming, probably. But take a Saturday afternoon and you’d have it. Personally I am a fan of momentum over KE. But like jeff says that doesn’t tell the entire story. Take a heavy but weak spine arrow and you could probably get better penetration from a lighter/stiffer arrow, even if it may have less KE. You have to compare apples to apples. Momentum is the tendency to keep an object in motion. The longer it is in motion, the more it will penetrate. The way I see it, the best compromise is shooting the heaviest arrow one can use, while still being satisfied with their arrows trajectory.