Good expansion has a low velocity threshold. The one starting 400fps faster will travel considerably farther before dropping below that velocity threshold.Not sure I understand this. You mean the slower one won't kill the animal, I guess the bullet bounce's off? Or do you mean the faster one will kill it deader? I thought the idea was to kill the animal cleanly, not deader!
Decreased drop and drift make it easier to put the bullet in the right place. The one starting 400fps faster has an advantage.
If all you’re doing is shooting whitetails at 60yds from a blind, sure, there’s going to be very little difference.
Why not hunt elk with a .222 Rem? The bullet will not just bounce off. No one said a 6.5 CM with 140’s wouldn’t kill an animal. YOU said there would be NO difference between a 6.5CM and 6.5-06, which is incorrect.