The best firearm to have is the one you have in your hand when the fecal material hits the rotating prop. Be it a .22 short or a .500 magnum! Honestly, caliber doesn't matter as much as shot placement. If you don't or can't hit your target then caliber is irrelevant. Personally, I prefer my Para Ordnance P14 loaded with 230 grain hollow points. Said P14 has 5,000+ rounds through it (it's my IDPA and USPSA pistol) and has NEVER failed to fire. EVER! My CCW is a S&W M&P Shield in (you guessed it) .45 ACP. I also own a 19011 in 9 mm. IMHO (and others that have shot my two 1911's) full load 9 mm has a sharper recoil than my P14 with full load rounds. I have never owned or shot a .40 S&W firearm but until last summer I did get to shoot a Glock in .40 S&W. I put 10 rounds in a 6" diameter at 10 yards as fast as I could bring the Glock back on target. The owner of said Glock said he never got that tight a group with it! When the FBI went to the 10 mm back in the 1990's, I got to shoot a Colt 1911 model 80 in 10 mm. It was THEE most PAINFUL pistol I have ever fired (and that includes a Ruger 3 screw .44 magnum!). IMHO, a 10 mm is not for the feint of heart or weak hands! Nobody so far has mentioned .380 ACP pistols. A good friend of mine (who is a VERY knowledgeable firearms person) carries a .380 ACP auto pistol. One of his fellow workers said, "I rather use my fists than a .380". My buddy replied, "Let me shoot you with my .380 till it's empty. Then you can use your fists". Fellow employee said, "jeeze, that wouldn't be fair". Buddy said, "then I guess a .380 is better than fists!.