i'm a 9mm man. the +'s outweigh the -'s (which aren't many).
the .40 does pack a little more energy than the 9mm, but, IMHO, that where the .40's advantages end (and high-quality +P 9mm defensive rounds close this gap in terminal results quite well, the .40S&W is already loaded to it's pressure limit in stardard loadings, according to SAAMI).
9mm is cheaper, is higher-cap in the same pistol, has better recoil characteristics in the same pistol and is more readily available. did i mention it was cheaper
? cheaper equals more practice, which equals more proficiency, which equals better real-world results.
the .357sig is a better performer than the .40S&W with the same capacity and recoil concerns, although even more expensive to feed . . . .
frye