RE: heart or lung shot?
 

Five of the six bull moose that I've gotten went down with the double lung shot (technically a bi-lateral pneumothorax) the shortest dropped in 15 to 20 yards and the longest was about 150 yards. Take out the lungs is just like removing 3 feet of a watering hose while it is running. Putting an arrow into the heart is like shooting the moter of the pump for your hose, does the job but takes longer. Actually. from the side it is more than likely that a heart shot would go thru both lungs anyway.

RE: heart or lung shot?
 

I will add that to take "only heart shots" from very high in a tree is pretty much assinine. The heart is so low in the deer's chest that at a high angle, you are having to simply "clip" a deer that is at close range.

RE: heart or lung shot?
 

Go for the lungs, you want to leave the heart intact so it can still pump blood for a good trail if needed. A heart shot will definately kill a deer but if it doesn't bleed fast enough you might not find it without a bloodtrail.