In regards to .40 & .45 ACP and 10mm & .45 Super, both seem to have similar, if not identical ballistics. So, when they are so similar is their any reason to choose one caliber over the other? Personally I have lots of .40 guns, but not one .45 semi auto. I do however have lots of .45 revolvers, but not one .40/10mm revolver, so I see the pros and cons to each caliber depending on what they're being shot from, but I really see no reason to suddenly up and buy a .45 semi auto or a .40/10mm revolver. What do you gentleman think?