I'll add to the pile here, but start with the short answer for those who want to duck out early. A slower heavier arrow (from my testing) aids in accuracy at known distances. The largest benefit you will see by going to your heavier setup is accuracy with fixed heads and forgiveness. Also, ignore KE because it's not a vector.
Deeper dive, I don't think you're getting caught up in the data, I just don't think you have enough of it. Things that most people don't like to discuss are drag and impulse. Because of our super small niche of a hobby, there's not going to be much data available for the builds we like to speculate over. So when we start with your "faster" arrow we're talking about an arrow that is faster by 8%. What does that gain you? Well according to your numbers "gains" you a negative 4% on your momentum calculation. Real world trajectory, it may gain you a few inches per yard after 50yds. This is something that I think we as archers and bowhunters need to do a better job of discussing when it comes to arrow selection. However, I think this will eventually prove to be a wash anyways because with an increased initial velocity also comes an increase in drag. (Fd=1/2pu^2CDA) Drag increases as velocity increases. What's interesting about this formula is it takes into consideration the surface area of the projectile with a fixed Drag coefficient, I say interesting because our arrows are far from having a fixed coefficient. We've all seen the paradox that arrow shafts experience, creating a dynamic coefficient at random distances until the shaft is stabilized. While surface area remains constant, the shaft is wiggling and writhing it's way through the air and bleeding energy due to it's shitty flight. So we rely on vanes to correct this, an increased velocity can create a larger distortion in these vanes (Check out the firenock vanes, Dorge covers this pretty well) As the vanes distort and compress the moment (torque) between centerline of the shaft and tip of the vane decreases, thus lowering angular velocity, thus lowering spin rate, thus lowering stability. Arrow stability (in my opinion because no one gives a shit enough in the scientific community to actually study this lol) has more to do with penetration than either of the two formula's you we're considering when we are talking real world applicability. A stable arrow is delivering all of it's energy through the centerline of the shaft, which is why MOST people shoot 3 fletch because they unknowingly do not have competing forces on opposite sides of the shaft. Putting all the speculation aside, everyone (whether it makes you feel good or not) should recognize that a heavier arrow (with all variables being equal) will always out penetrate lighter arrows.
Skipping over impulse, but a heavier arrow will allow for more energy to be conserved. Longer lock time through the bow, and more resistant to exterior forces.
So let's come full circle on this, what is the real world POI shift you are seeing between the two arrows? A 460gr arrow with a velocity of 290 will impact 1" higher at 20 and 2" higher at 40 when compared to a 512gr arrow at 272 for my setup. When I take into consideration my shooting ability at 40, the two arrow groups will have a 1" overlap most days which makes this comparison a wash in my mind.
Is the 4% increase in momentum going to save your ass on an animal? Doubt it
Is the extra 8% in initial velocity going to limit your yardage errors? Doubt it
Heavier arrows at slower velocities are more resistant to forces and seem to stabilize faster. (There's a reason why most people claim fixed blade heads tune "better" at lower velocities)
Thanks for letting me rant