I've told this story before, but my love affair with the .40 S&W cartridge started by complete accident.
Up until late 2019, my primary carry cartridge was .380 ACP, which I felt was completely adequate for two-legged threats and still do. However, in late Summer of 2019, Hogs started venturing out of the woods surrounding my residential area and suddenly .380 ACP just didn't inspire as much confidence as it previously had.
Problem was, I was flat broke, in a poor financial state, and thus couldn't afford to go out and buy a new 10mm Pistol as I had been recommended. One day when I was at my LGS, I saw a S&W SW40VE in the case priced at $199 and immediately asked to see it. The pistol felt good in the hand, was small enough to carry concealed, held 14+1 rounds, and was obviously a far more capable pistol than my Ruger LCP. So I went home and did some research on the pistol as well as the cartridge, with the most decisive information I found being that the .40 S&W was actually the issued round at the time for Fish & Game in my area. The very next day I went back to the shop, put the SW40VE on layaway with, picked it up a couple weeks later once I had the money, and promptly began carrying it.
My first trip out to the range with it yielded surprisingly results, as I was expecting "snappy" recoil as I so often read online, only to discover that it actually had substantially less felt recoil than my Ruger LCP and was comfortable to shoot by comparison.
After that, the .40 S&W became my favorite pistol cartridge. I had previously fired pistols chambered in .38 S&W, .38 Special, 9mm Parabellum, .357 Magnum, .45 Colt, and even .410 Bore, but .40 S&W felt just right to me with enough recoil to be reassuring without making it difficult to stay on target.
Now I own multiple pistols chambered in .40 S&W and love them all. My most recent acquisition was a Beretta 96 Centurion, which was initially met with people telling me how the 96 couldn't hold up well to a steady diet of .40 S&W, with many recommend that I convert it to 9mm. However, after some research, I discovered that simply swapping out the factory 14lb recoil spring with a heavier 18lb Wolff spring and tossing in a cheap little Wilson Combat Shok Buff was a common means of making it last longer. Subsequently, I got a .22LR Conversion Kit for it as well.
I've had many different people try to convince me that I'd be better served carrying a 9mm, how its what the FBI carries, how it performs no better in gel testing, how "modern technology" has made 9mm as good or better, but I just plain like .40 S&W. Besides, for all the arguments I've read about how that larger stretch cavity doesn't do anymore damage than 9mm, I've yet to see anyone attempt to make the argument that it's no more painful and therefore no more likely to deter an attacker.