RE: which bullet to use??
 

I think you should drop the idea of dropping them in their tracks! As so many others have said, a lung shot is not really expected to put them down in their tracks.

Raising your aimpoint to try to hit spine is a foolish notion in my book. Doing so lowers your margin for error if you don't hit where you are aiming. Shoot just a little too high and you miss.

Bullet type is not going to significantly alter this equation. Bonded bullets, in my experience, kill deer less quickly than non-bonded bullets.