2010_FX4,
I carried the Glock 31 on duty from 05/02 - 08/09. I shot 60k rounds, that's no typo, 60k rounds, through it before I sheared the lug off of the factory barrel.
The gun had previously broke the left rear slide rail off, so it made two trips to GLOCK during its life.
When I got it back the second time, it had three different serial numbers, the original one for the slide, and a new one for the new barrel, and a new one for the new receiver. I sold it and switched to the 40 caliber with no regrets.
.357SIG is a potent round. Interestingly our department no longer authorizes it as a duty round, in part to surprisingly lackluster ballistic testing we did in 2008.
We had been using 127 gr. +p+ Winchester Ranger T ammo in 9mm which chronographed @ 1250fs. The 125gr. Winchester Ranger T .357SIG round was only 75fps faster @ 1325fps and performed worse (less expansion & penetration) than the 9mm ammo. That coupled with how it beat up our Glocks (all our SWAT guys were carrying the 31) made the decision to transition to the Glock22/.40 cal an easy one.
I'm not sure you remember, but when Remington came out with the round in 1994 it was rated at 1425fps, a real screamer, but soon after, very much like the 40S&W round, was detuned.
We primarily use the .40S&W & .45ACP, both in Federal HST (the .45 being +p). I rate them as the top dog in ammo now.
Now, in a Sig-Sauer, which beefed up the 226 .357SIG considerably, compared to their 9mm, it will have no difficulty handling the round. I just have lost interest in the modern offerings of .357SIG, even in HST, believing they offer little true ballistic advantage over 9mm, in standard, +p, or LE +p+, or .40S&W. That coupled with much higher shooting cost would make me lean towards .40 if you are not recoil sensitive (and I doubt you are) & 9mm if you are.
Just my 2¢.
Take care,
Gary