If a deer is facing me, or has his neck turned toward me, I'll go for the center of the white spot. I've never seen a ruined volume inside the neck much less than about half my fist, so that's aorta, throat, spine...I use the Sierra 85-grain HPBT, and that's why I'm picky. But, it's like delivering a mini-grenade.
Pretty much side-on view of the neck, I want the center or a smidgin higher. Again, I don't have to exactly hit the spine for the animal to be at least down and paralyzed.
Quartering, I'll most likely try for heart/lungs.
The only buck I ever headshot, when we were hanging him by his horns back in camp, his horns folded up. Ruined the photo.
The majority of my '06 shots have been to the heart. Mostly because of generally longer distances. No point in maybe missing. But, that's mostly walking hunting, with the '06, and offhand shots. Sometimes at running deer, and trying for the neck is rank optimism.
Art