You will be fine with any of the quality hunting rounds off the shelf. Deer are not hard animals to kill. While I agree that the diameter is important, where you put that diameter whether it be a .22 or .512, is way more important than its size to me. I love the 44. I love the 45. I've killed more with the 44s than the standard 45 over the years unless you pull in the 454 which severely tips the scales in favor of the larger caliber but in the standard rounds, I've never felt undergunned with deer and hogs with a 44. I killed everything from squirrels to elk with the 44. It was what I started with first and for that reason, I'll probably always have a soft spot for it. For some animals though, the bigger calibers with appropriate slugs I think definitely have their place.