I'm a keyboard quarterback, like most of you. I've spent more time researching and analyzing service calibers and handguns than I like to admit, and I think the links in my signature show that. It's been an evolution in many ways. Through my own experience, research and reasoning, even a little maturity, here's what I've come to believe: 1) My CCW caliber needs as a citizen are not the same as LE (e.g. I do not expect to shoot through much auto glass). Also, gun size very much matters as I must CCW not open carry, so won't/can't tote a full-size "duty" gun. Intended application matters. 2) In optimal service loads, 9mm, .357sig, .40sw and .45acp are all adequate. 10mm trumps them all; 45 Super even more still. Load Data 3) There is a performance difference in 9mm, .40sw and .45acp. They are not equal, but they are comparable in that they are all adequate and it's a scale from good-better-best. Comparing the average performance of optimal loads in each, I believe, based on optimal selections in each, 9mm to be at best 95% of .40sw and at best 90% of .45acp, and the .40sw to be at best 95% of .45acp. (Data: Load Data, Caliber Data % & Caliber Talk) Those are greatly simplified percentages, but what I've observed looking at aggregate data. The main point: To me, the difference, whatever it may be, matters less to me than it once did. 4) Selecting a CCW ..... 1) Cost (my budget has limits) = Good: .45acp; Better: .40sw; Best: 9mm (lower ammo cost = more shooting; see #3) ..... 2) Reliability = Tie. One reason why I chose Glock: Why Glock | A Glock is a Glock | Your Glock Experience? ..... 3) How well I shoot the gun = Good: .40sw; Better: .45acp; Best: 9mm ..... 4) Ease of maintenance/use = Tie. One reason why I chose Glock: Why Glock ..... 5) Size of gun (I prefer mid-size guns to shoot, small size for CCW) = Good: .45acp; Best: .40sw/9mm ..... 6) Capacity = Good: .45acp; Better: .40sw; Best: 9mm ..... 7) Caliber = Good: 9mm; Better: .40sw; Best: .45acp (Load Data, Caliber Data %, Caliber Talk) 5) The odds caliber will ever matter for me as a cautious citizen are incredibly slim. Do the math and citizen caliber selection (for almost all citizens) is for peace of mind through the idea of greater security. Example, for conceptual illustration only: ..... 1) Likelyhood as a cautious adult male citizen in rural or suburban America that I'll ever actual NEED my SD handgun in my lifetime: .0001% (note: this % is once in 20 years) ..... 2) Likelyhood I'll even have my SD handgun when/if I do actually ever need it: <25% (My time: work (no CCW) = >25%; home (w/ shotgun) = >50%; CCW = <25%) ..... 3) Likelyhood just presenting the gun will end the threat: 90+% ..... 4) Likelyhood I'll hit my target COM: <40% (police shootings <40% hits) ..... 5) Likelyhood I'll make a shot where a 5%-10% difference in performance will even matter: <5% ..... 6) Likelyhood my greater speed/proficiency with 9mm follow-up shots will even matter (average gun fight less than 3 shots, directly effects #4): >5% ..... 7) Likelyhood my service caliber selection will ever matter: Result of #1-#6. Happy shooting.