IMHO, .357 sig can do nothing better than its parent case, the .40, which is quite a good round. The ONLY advantage in .357 sig that is touted that I see some merit in is that the bottle necked case might feed a little more reliably, but I have straight case ammo that are 100 percent, won't keep one that ain't.
It is NO .357 magnum, though. It does produce velocities within 100 fps of what I can get out of a 4" .357 firing hot 125 grain hollowpoints, but I like 140s for carry in my 3" magnum. The .357 magnum is a better field carry and hunting caliber, of course, due to its versatillity, .38 wadcutters for small game to 180 grain hog stompers for hunting and critter defense. With a 6" barrel, the .357 magnum is up there with the 10mm for power, far out paces the sig round, but the .357 magnum is sensitive to barrel length due to the bulky, slow powder of the big case. As a defense gun, .357 sig is fine, but so is .40 or .45 or 9mm +P or .38 special. I often carry 9x18 Mak and feel very confident with it.
So, as you might gather, I'm not a .357 sig fan and AM a .357 magnum fan. I do like my revolvers. The sig round is more of a marketing gimmick, came along to talk agencies that had carried the .357 revolver for years into carrying a 9. Call it a .357 and they'll come. It's a 9mm after all, .355" bore. And, in fact, 9mm+P+ come pretty danged close, though I wouldn't carry any +P+ round, myself. 9x21 will get her done, though. But, the DPS likes that ".357" moniker, so Sig's marketing did the job,. I reckon.