People often forget that a deer's brain is very small in comparison to its head. I've never been a big supporter of taking head shots because so much can go wrong YMMV.

Having said that, the evidence is quite clear on the performance difference of the two projectiles. If you are going to take a head shot you need a projectile, and velocity, that'll do massive damage. If you take heart/lung shots then a projectile that holds together better for deeper penetration will be better.