Your test is way shy on data to draw meaningful conclusions. As I got older, and over almost 50 years killed many big game animals and watched lots of others others shot as well, in grading these two types of shots I get “I dunno.” I’ve seen bull elk drop immediately with a lung shot, and have seen them move off a hundred yards or so before dying. Similar with whitetails, mule deer and caribou. Even antelope. I have had a heart shot mule deer go down immediately, and a couple others run a death circle of from 50-90 yards. I am likewise dubious of grading shots/cartridges/bullets by the speed at which an animal expires.
I think it helpful if the bullet exits, but I’m not sure I can prove that one either. As somebody else said, I consider the heart/lung area to be one target, and center of mass means usually a lung shot. I also feel better about a bullet that I know will drive through a shoulder if necessary to get to the heart/lung area.
As in many other things, the older I get the more cynical I am about conclusions.
