For me using a gun, the best shot placement is just behind the shoulder and 1/2 way from the top of the back to the bottom of the chest. A double lung shot is just as quick in bringing down an animal as a heart shot (in fact usually quicker). And if you miss forward you get the shoulder, down the heart, up the spine, and back the lung/liver.

I have seen more lost deer from people trying only for the heart than a lung shot. Of course, we are talking about a standing broadside shot.

For a bow, the double lung shot is the best way to go on a broadside animal.