I came back to re-read the posts and all I can say is "WOW!"
A few parting shots:
When a Sig P229/357Sig was first pressed into my hands I shot the qualifying course as well as I did with the Sig P228/9mm. The only way I had to determine trajectory was to shoot at increasingly distant targets with each gun and note point of impact. The 357 far outperformed the 9mm.
Ammo we trained with, 9mm, was at least +P and, by my imperfect memory, more like +P+. I most remember that after shooting it, American ammo seemed like puff loads. 357Sig really tromped those.
I used and continue to use 357 guns in competition where nearly everyone else uses 9mm. To be sure, age has slowed my hand and "re-aimed" my eyes. Still, there is little difference between my performance with an M&P/357 and my M&P Performance Center 5" 9mm.
.40S&W. I can think of no good reason for it, but of the 9mm, .45ACP, .40S&W and 357Sig, I shoot the .40 the worst of all. Kind of annoying because I reload .45ACP and 9mm, and used to load .40S&W, but I gave up reloading 357Sig because I messed up too many shells. I buy custom commercial reloads and watch for sales.
Until this week I had been shooting my M&P357 better than my Sig P320C. Then, upon carefully reading a lot about the Wilson Combat grip frames for the Sig P320, I bought one. I set up a 5-target stage requiring shooting 50-degrees right and left from ~5 yards, then ~10 yards, and ~15. My goal was two rounds in a 2"X2.5" oval in the "head" of each target. Ten rounds per stage. I fired a P320 with the Sig frame and a P320 with the WC and was astounded to see I was 1.5 seconds faster and with comparable accuracy with the WC . The difference, clearly, was in how quickly I could fire the second shot.
So, for me the caliber is alive and well. I've had excellent service from Storm Lake barrels and if I needed to convert a newer S&W to 357Sig, that is what I would use. Thing is, I now have three M&P/357Sig (two LEO turn-ins), and two Sig P320c/357Sig. I bought a Sig caliber conversion kit in 357 and stuffed it in the safe, for someday.
I appreciate all the input to this thread. I enjoyed it and learned something. SDH