I agree, its always going to be about personal choice and experience. You have to do what you have to do to be happy. By all means, use what you like and shoot with the best.
The muzzle blast and flash of a .357 Magnum are vastly over-exaggerated and really only an issue with the hot 125grn Magnums like the famous Federal 357B.
The muzzle blast and flash I'm accustomed to from the 357's was more from the older 125 grain loadings, fired from shorter barreled guns. The whole point of them was because they were "hot", and it was accepted that there was going to be blast and flash. Some of the newer loads do have more reduced flash, but the blast is still pretty impressive, and again, especially from the shorter barreled guns. The punishing recoil of the smaller guns was also something you had, and still do have to deal with. With the 357SIG, you get neither, and you dont have the shootabilty issues with the smaller guns.
Also, I think you're underestimating the number of people who are carrying revolvers. S&W K-Frame .357 Magnums, particularly models with 2 1/2 or 3" barrels are becoming increasingly difficult to find and expensive.
I think the main reason for this is, they are not normally an item you see in most shops and have to be special ordered. Prices on most of the new revolvers have gone up like everything else too.
I think this can also be said for most model revolvers these days, they are just not as popular as they once were, and other than the J frames, you just dont see them in the cases in the numbers you used to, or at least in all the shops I visit, and what you do see, are the occasional new model or your basic trade in types. If you want something specific, your chances of finding it on the shelf are pretty slim, and you usually have to order it.
As far as underestimating the number of people carrying them, I come in contact with a lot of people who, be it for work or otherwise, carry guns, and I personally know of no one who carries a revolver larger than a J frame, and those that carry them, use them mostly as back ups. My buddy owns a pretty busy and well stocked gun shop, and the J frames and cowboy guns are the big sellers when it comes to revolvers. Most of the other revolvers on his shelves are trade ins or collectibles. The big sellers in the shop are the 1911's, XD's, Glocks, and SIG's. I'd be willing to bet, if you go into most any shop, the autos out sell the revolvers by a fairly, if not, very large margin, but especially when it comes to a weapon that will be carried.
Your experience is quite different from mine. I actually find a revolver easier to conceal than a similarly sized auto because, for the most part, the more rounded contours of a revolver make it less likely to print,
I suppose its again all a matter of preference and how you carry. I've always found the autos (along with their reloads) to be easier to hide and more comfortable to carry, especially in an IWB type holster. I dont normally use anything else, and the OWB, while more comfortable with the revolvers, mostly due to the cylinder issue, requires more work and effort the keep the gun hidden due to things poking out.