Shot placement trumps all else.
That said, a fast-opening bullet that also has enough azz to punch through and leave two holes for leaking blood is very helpful, as is the spray of tissue and blood and hair that gives solid evidence of a hit at the spot where the deer was standing. Also helpful are holes low enough on the body that blood accumulating in the chest will begin to drip out and leave a trail. There are lots of bullets that can do the job now and weight need not be much of a factor, except maybe for straight cup & core designs.
The buck I killed in 2011 was hit center-chest, tight behind the shoulder with a 130gr Hornady IL, which didn't exit, but did knock a clump of hair off the far side of the chest. The deer ran about 150 yards without leaving a drop of blood even though his lungs were totally souped. A lower hit or a pass-through would have given me a blood trail to work with instead of just tracks in the leaves.
