Both lungs for me too
And the head shot was just one of those options I didn't really expect people to answer...
I do aim small miss small. But, if you happen to miss big ( 3-4") @ 20 yds with bow you can easily miss the deer but, if you're aiming for the lungs you can still clip the bottom and maybe hit the heart by chance. The adrenaline of the deer is over in seconds. 15 seconds is a long time for a lung shot usually you're looking r around 5 seconds on a good solid lung shot.