I guess there are many variables to cosider. Angle down and angle away and the list goes on. I typically try not to focus too much on it when I draw and aim. I'm looking for nothing more than a vital shot of either caliber and thinking too hard about it before the release may actually cause a more unsure shot. The way I see it either is fine,but one may realize that if the heart is hit it may not mean a quickly downed deer and even though the heart may not be working any longer the deer may continue it's run and with the heart not pumping the blood no longer is and could mean little or no blood trail. With the lungs the deer may run long but as the lungs fill with blood and with each breath the deer takes and releases it also releases alot of blood to follow. Just my spin on it.