"***best for stopping power in a CCW."
Among the calibers listed, my choice would be the .45 acp, but you're really doing yourself a disservice unless you try out a few guns in each caliber to see what you feel comfortable with (you didn't specify the particular pistol envelope you're considering). And you really ought to consider something in 10mm too, either the Glock 20 or 29, depending on which fits your hand, or, if available, a used-but-decent-condition "Commander"-size Smith 10mm (1066/1076).
Quite conveniently, the Glock 10mms are 3-in-1 guns, having the ability to take aftermarket barrels in .357 Sig
and .40 S&W without the need for buying anything extra, like mags or springs. Just swap out the factory 10mm barrel and drop-in the .357 or .40 barrel, and you're up and shooting another caliber. The cost of the extra barrels
together is still cheaper than the cost of a new gun in either caliber alone.
So now you've got 2 of the calibers you originally listed, plus the 10mm. Just leave in the barrel of the one you feel most comfortable with when doing CCW.
Getting back to the .45 acp: it's available in a wider variety of bullet weights/load configurations, at least in my area, than the .357 Sig, as well as being cheaper. While the .40 Swishy-Walker is certainly plentiful on dealers shelves, the .45 wins hands down for accuracy. When I shot the .45 more extensively than I do now, I really liked the 185gn+P JHP load. The 200gn HPs are also great loads.
Again, different pistols - their shapes and ergonomics - are going to
feel much different even if they all shoot the same caliber. It's more than felt-recoil; it's a combination of the pistol's weight and balance and it's pointability too. So, in the long run, it pays to rent a bunch of pistols
before you buy. Hopefully, there's a well-stocked gun range in your area.
