Interesting question. Im not sure that bullets of similar construction would show one killing any faster than the other. Of course there isnt any way to test that theory. I personally think the hydrostatic shock thing is mostly hogwash. Its my belief that destruction of tissue and bone is what kills deer. Im sure the shock has some effect, but I just dont think it is the primary factor in killing. If we're talking about conventional lead core designs, and similar velocity ranges, the bigger bullet gets my vote primarily because it will dig in deeper and destroy more of the critter's parts.But your example of a 3006 with 150 and 180 gr bullets might actually show more tissue destruction with the lighter bullet since both of them would penetrate completely on the shot you described, and the lighter bullet would have higher velocity and more violent expansion. It seems to me that the really tough bullets like barnes x , failsafe, and bonded cores and the like work better, that is kill quicker at higher velocities. Who knows? I think we need to shoot about 100 deer with every bullet made and keep careful notes. Then we still wont have an answer. Its always shot placement that becomes the deciding factor. Thats the one variable you always have control of too. If you want your deer to die in his tracks the broadside lung shot wont always do it no matter what kind of bullet you use. I guess my answer is "I dont know". Another thing you can never know is whether or not its easier to kill a deer that is relaxed or excited. One that is full of adrenilin might not go down so quickly. This is one of those topics that can be categorized as "significant, but meaningless" heh heh, Maybe some others here have more decided opinions about this.