Haven't read the whole thread but,
Put a poor bullet (fmj, AP, etc.) Into the correct area (heart,lungs or brain) and the animal will die. It may take some time but it will eventually happen. Conversely if you put the best bullet (accubond, aframe, sst, etc) in the wrong spot (hoof, leg, etc) the animal could well survive.
Of course the best idea is to put a good bullet in the correct place, this then results in a quick clean kill.
So I guess that's my long winded way of saying yes shot placement is more important than the bullet.