With aiming points I'd suggest that the circumstances of species, distance, what can be seen of the animal, the rifle and cartridge, the shooters skill, is the animal about to flee in fright, the time for the shooter to locate and aim at a vulnerable part of the animal, the intangibles of buck fever/nerves/self confidence/excitement all play a big part in the successful downing of the desired animal. There is one more point about aiming and that it is essential for the hunter to have a solid working knowledge of a deers internal anatomy. Many do not.
I'll confine my comments to those elusive shadows of our heavily vegetated and steep Aussie bush - sambar. Over decades of studying this deer species I have learnt from them how to move, when to move, the 'right' camo clothing including face mask and gloves and working with the breeze direction. All combine so that the chances of detection are reduced to almost zero. For years now I have reduced the distance between me and an unalarmed sambar. My usual aiming point is a frontal throat shot. But not just anywhere on the neck front. The aiming/impact point is a hands width further down from a sambars head length . This is critical because at the last second the deer may drop it's head and obscure part of it's throat. If he does that...and they are notorious for sudden movements...as you fire then the result will be a deer with its face shot off and sentenced to a painful, lingering death.
Distances from me to the sambar are very short...much more so than most would expect. A long shot for me is around 20 metres and normally fall into the 6 to 15 metre distances. No hold over to compensate for bullet drop needed...hehe. Calibre and bullet choice depends on my mood on the day and location but I'll leave these matters alone for this thread.
When I hit a sambar with a throat shot without exception it instantly rears up on its back legs and does a full backward somersault. Dead before it hits the ground. The damage is impressive.
I tend to leave other aim points alone and wait for my preferred hit point to be available. In the past I have used a chest shot but where I aimed depends on the rifle and calibre in my hands. I don't have to rush and settle for a second best aim point because the deer is not alarmed and not going to run off. More than a few deer hunters aim at the back end of a rapidly departing sambar but invariably they either miss or wound it. I also strongly dislike the frontal chest aiming point at a deer which is standing still facing the shooters location trying to work out what that noise was that it heard. It is a mortal shot but allows the deer to run off and often well beyond the shooters ability to track it down. Again.... more of this tracking caper some other time in a suitable thread.
Anyway...it's bed time here so I'm off.