RE: For personal defense: 40s&w vs 357sig
The NC Dept. of Corrections recently switched from S&W model 65 revolvers (.38 cal.) to the S&W .40 cals. Many of the female staff have commented that the gun was much easier to control and get back on target during timed firing. Many of them also stated that they shot their highest score using this weapon.
I don't have any experience with the Sig so I can't comment on that. ~sorry