357 sig is a rimless necked down case it is necked down from a 40 S&W for use in a Auto. The 357 Remington is a rimmed straight wall case for mainly for use in revolvers the 357 Sig and 357 Remington mag are not interchangeable

Sig Sauer and Remington both make .357 MAGNUM rimmed case ammo used in revolvers and some rifles. The round called the .357 SIG is a rimless case made for semi-automatic handguns. The .357 SIG gives you opportunity to shoot an auto that makes very near .357 Mag power. There are autos that will shoot rimmed .357 Mag cartridges (the Conan, Desert Eagle) but they are really big guns and would be hard to carry. But the newer .357 SIG guns are in made in sizes that make good everyday carry guns.

Bruce, not much if comparing the same bullet weight in both. They are rated the same velocity and energy wise. The cost difference is strictly a Brand issue. Cheers and stay safe!