Ammunition price, muzzle report/blast, wear and tear on firearms. 9mm and 40S&W offer similar performance with the right rounds. Check out Winchester ballistics testing on the various duty rounds and you will see there isn't very much difference (penetration and expansion,) between the 9mm, 40S&W and 357 sig.
I have years of experience with the 357 sig as an issued duty round. During training on an indoor range I developed headaches and some officers developed a flinch. I had to use double ear protection. Not a bad round indeed, but not worth the extra cost over the other calibers IMHO.
Last edited by Noreaster; May 27, 2012 at 10:25 PM.