There are all kinds of theories as well as conclusions. If you have a speedy bullet, say a 150gr from a .30-06 then you will have, depending on bullet design, the best of both worlds usually. Bullet expending a ton of energy and creating a massive wound channel while still retaining enough energy to pass through. This way, if you have chosen a particularly tough animal, you will have a good blood trail as 2 holes are always better than one.
Then you have the "big and slow" crowd which like to have a big bullet of a less tough design for easy expansion then plows right on through creating sufficient damage internally but still bulldozing it's way on through the animal.
Typically, most hunters like pass through performance. I am one of them. My choice of shots is high shoulder seen here:
Placed correctly, this will drop an animal in it's tracks. If you miss low, then you are still nailing lungs and possibly heart as well. Miss high and you will be more than likely missing the animal entirely so no walking off injuries. A perfectly placed high shoulder shot not only interrupts spinal function, but also takes out the lungs.