The .45 colt served the U.S. military well for seven decades until the PC weenies forced adoption of the "Nato" (Nazi) 9mm.
After all two World Wars proved the Luger's "superiority" ..well it looks neat but the old Colt will take a man down quicker.
The .45 acp usually has TWICE the bullet weight and is much larger diameter resulting in more damge . .45 can also be procured in the various exotic hollowpoints and special expanding but the "rules of war" , the 9mm is really just an European .38 .