i like the 9mm.. but anyway, i said this on another thread, maybe a different forum but i will say it again.. with each handgun design (or any firearm design) theres a limitation as to what they can handle.. in most weapons this limitation is the bolt thrust which is basically the surface area of the inside of the base of the cartridge multiplied by the pounds per square inch produced by the ignition
the 40S&W and 9mm standard pressures generally are about the same, with the .40 having a larger base diameter it means its going to have a greater amount of thrust, meaning it will be more abusive to the frame, slide, slide stop, etc.. so if left at standard pressures the 9mm chambering in the same pistol will generally be less taxing on the weapon itself.. however, this also means you can push the 9mm at much higher pressures than the 40S&W without increasing the bolt thrust beyond what the .40 puts out... im talking +P and +P+ stuff that if loaded the .40 to those pressures would probably wreck your weapon in a relatively short amount of time.. figure with roughly the same inside case diameter, a +P and +P+ 40S&W is putting out MORE bolt thrust than a 10mm
so with newer pistols focusing on being able to handle the increasing pressures of hotter 9mm loads, we're able to push 9mm so hot that it can actually match, or at least come VERY close to what the .40S&W and .45ACP put out without adding more stress to the weapon than these other cartridges... take that into consideration plus the higher magazine count, faster follow up shots, the 9mm is by no means no slouch and anyone who believes it is is quite simply VERY misinformed