I would be talking (from my experience) exclusively of impact velocities well over 2000 feet per second. Our big game shots have always been under 600 yards, most in the 300-400 yard range. Whether the thickness of the hide of an elk is only millimeters more than a deer or not, I have personally seen more bullet pass through shots on deer sized critters than on elk, and have seen deer sized critters fall quicker with the same bullets than an elk with similar shot placement. My limited personal perspective (fewer than 30 deer and 7 elk in the past couple years) indicates that I would prefer a bullet that retained a bit more mass, and best case even gave me an exit wound for better blood trails on the bigger critters. We havent lost one yet... knock on wood... but were we ever to have a situation where we took a shot at an elk at the edge of thick timber, if that elk has even 30-60 seconds to travel before it expires, it could mean the difference between finding it or not if there is no blood. Considering that even with PERFECT shot placement, one of these critters can still go miles, I need all the help I can get.
I never will forget the time when my friend shot an antelope buck with his bow. Shot placement was obvious, and perfect. The buck laid its head down, and appeared to expire on the spot. We thought GREAT! job done. So, we stood up from our concealed position... and apparently the buck wasnt done for. He stood up, and followed several does over the skyline. Ended up tracking him for over a mile. My friend put one more arrow in him. When we were gutting the buck, we found the first arrow hole (complete pass through mind you) and a perfect broadhead shaped hole through the center of its heart. No joke! It went over a mile, and over an hour of time with a broadhead sized hole in its heart! Bottom line, I need every advantage I can get to ensure that my bullet does the job, and even when conditions mess it up a bit, I still need to find the animal.