I as well believe that a "vitals" shot is the best shot for a kill shot.

A shoulder shot mainly hits the scapula (shoulder blade), and may cause the bullet to fragment severely not allowing penetration into vital organs, or arteries.Yes this does mean that the bulletfully transfers its energy into the animal, but will mainly cause tissue and bone damage.This will handicap a deer, but not necessarily kill it.

A neck shot is even more difficult to ensure a kill shot. A neck shot will only kill a deer if it severs and aretery/vein, colapses the trachea, or contacts the spinal column and thereby spinal chord. All these anatomical features are closely spaced, and a very narrow target to hit.
As you can see in the following picture a deers spinal chord is nearly centered within the neck musculature. This needs a very well placed shot to hit.



I personally only use neck shots as a final, point blank finishing shot for a deer that is already downed, and unable to stand.

Like many have stated the large area behind the shoulder ensures a large killing region, large numbers of vital organs that when damaged are lethal, and the thin tissue layers and ribs allow the bullet deep penetration.

I vote Vitals.