The .357 Sig was designed to achieve .357 Magnum performance in a conventional auto pistol. Up until it came along about the only gun that could accomplish that was the Coonan Arms .357 that was built along the lines of a modified 1911. It has become somewhat of a collectors item. I heard it is back in production, but I've yet to see one for sale anywhere.
The .357 Magnum achieves 97% one shot stops with 125 gr. Jacketed Hollow Points for those who put faith in such things. I think that is what they were trying to replicate in the evolution of the .357 Sig. It does have a good selling point with it's interchangeability with the .40 S&W. With the popularity of auto pistols in the self defense market, I think it is a round that will have enough of a following to keep it around, much like the .41 Magnum has in the high powered revolver market. I would consider getting one, but I don't shoot the .40 S&W. In auto pistols I stick with 9 MM and .45 ACP. If I want .357 Magnum performance I have several revolvers that fit that category nicely. I am not one who believes the wheelgun is destined to disappear like the Betamax and the 8-Track tape player. At least not anytime soon. But as for the .357 Sig itself, much like most of what we own, it is a nice want that does not require to be justified as a "need" to purchase. If you like it, go for it and enjoy it. And as far as the Glock it comes in, well let's just say how can you possibly have too many Glocks? Bill T.