These threads always make me laugh..
I'm willing to bet most of the people arguing which round is "better" have never killed anything with a fire arm in REAL LIFE! Ballistics gel doesn't mean diddly, live targets have skin/fur, clothing, fat, and bones, that being said, all modern calibers are adequate.
I hunt almost everyday during the season and get to see firsthand what firearms can do. Duck hunting for example has a wide variety of hull length, powder capacity, shot size, shot shape, shot density, shot capacity, and velocity. And with out getting in to specifics I will tell you they all work. Some at further distances than others, but within a reasonable range they all work the same. For ducks I use steel #4, and find it kills ducks just as well as #2. It has way more to do with where you hit the bird then it does shot size. You want to drop something dead where it stands/flys, shoot it in the head or neck. I've shot birds straight in the chest with tungsten, only to have them fly off and drop 200 yards down the river. A vital hit isn't always a stopping hit. The same is with deer hunting, you don't need a .30 caliber round to kill, just a well placed shot. In Europe, the most popular non belted magnum round is the 6.5 Swedish, and kills plenty of moose every year efficiently. Here in the USA people use the .243 and harvest just as many deer as people using .30 cal offerings.
The same can be said for human targets. All bullets create trauma, but that is not what kills something immediately, although more trauma means a bigger wound, which translates to blood loss, but it could take a day to bleed out. Shoot someone in the head with a 9 they'll be the same amount of dead as with .45.