I HAVE a Sig P229. I could really get into an ammo cost issue and just get the .357 Sig barrel for it. I tried someone's .357 Sig and was expecting more recoil, reminiscent of the .357 magnum revolver. To tell the truth, couldn't perceive a difference between it at a .40.
The .40, ballistically, isn't THAT much better than a 9mm. But a .357 Sig has quite a bit more to it.
Speer Gold Dot, fer instance, the data looks like:
.357 Sig 125 GR 1350 fps 505 ft.lbs
.40 SW 180 GR 1025 fps 420 ft.lbs.
9mm 147 GR 985 fps 316 ft.lbs.
.38 +P 125 GR 945 fps 248 ft.lbs.
And I am most likely to be carrying the .38+P equivalent. To switch to a .357 Sig, I'd have a bit more in holster. With not much more felt recoil. Can that be right? Bah! I grow weary of my own spouting at this point and must ground myself.
Power of the cartridge is not the be all end all, of course. Of course. If I may quote:
"Way more important than caliber, even more important than readiness condition of your sidearm (with the caveat that if you're carrying for self-defense, it should be ready), is if you are ready."
Trudat. What she said.