As hunters it seems to be a paradox that we want to take the life of an animal, yet we (and perhaps this isn't true of all hunters, but the vast majority of them it is) want the life to be ended painlessly, quickly and to that end, there is a lot that goes into our planning.
One of the tid bits I have been mulling over in my head the last few years is new information concerning single bevel broadheads. It is a topic of discussion, at times bordering on heated debate among traditional bowhunters. Ongoing research has been spearheaded by Dr. Ed Ashby, a retired optician out of Australia.
In a condensed version, a single bevel broadhead twists into the animal, using the forces created by the single bevel to cause quite a bit of torque.
Because of the torque, it has been shown that it can cause bone breaks in critical near hits on leg and shoulder bones. It also effectively creates a larger wound channel in soft flesh by creating a "wrapping" effect as it is twisting.
I encourage you to read a bit about the doc's research here.