Originally Posted by David LaPell

The .357 Sig isnt as popular as it should have been because it didn't deliver on it's ballistics. Sig Sauer created the .357 Sig to be an equal to the .357 Magnum so the shooter would have the power of the Magnum in a pistol. It didn't happen. Don't get me wrong, the .357 sig is a great round, but the .40 is better and if you can the same size gun with more power, well which would you choose?
The 125 grain Hornady XTP in a .357 Magnum is 1,500 fps and the 124 grain XTP is 1,350 fps. It is still a good round though, better than the 9mm.

I did this one a while back. Don't get me wrong, I like the .357 Sig and will probably buy one someday, but it just didn't live up to the hype.

Noble Experiment meets Tried and True: The .357 Sig versus the .357 Magnum - Gun News at Guns.com