If I was good enuf in a hunting situation to place an arrow precisely where I wanted to, I would go thru the big vessels/arteries just above the heart, which would also take out both lungs in the process. I think having the heart intact and pumping helps with a good blood trail and fast bleed out. In the few times I've been lucky enuf to get this hit, it has produced the shortest and heaviest trails of all. When I can follow the trail from the tree, I figure it's pretty good.
A sharp broadhead thru both lungs and any critter is down. Seems to me that the closer to the center of the lungs that broadhead goes, the quicker the critter goes down.
I also agree with those that feel most 3-D targets are marked too far back. That's one reason I rarely shoot for score.