No it doesn't. Factory American Eagle .357 Mag from a 4" GP100 vs 16" Rossi. 1318 fps vs 1799 fps. ~480 fps change just due to barrel length. Also that's a heavier 158gr bullet (and a practice/plinking commercial load). A 125gr would do even better with longer barrels due to the extra powder.

That said, in a longer barrel, no doubt the .357 Mag will outperform the SIG in terms of energy. It has more case capacity. And it can push heavier bullets. But if you are using a 125gr bullet, and a pistol as short as most SIG's, you'd be hard pressed to push the bullet much faster.

Keep in mind a 4" SIG has 4" of chamber and barrel. A 4" .357 revolver has 4" of barrel, and about 1.75-2" of cylinder. It is a substantially longer gun than a semi-auto 4" chambered in the SIG round. You'd need something more like a sunb-nose to get similar size (in length, obviously the semi will be thinner no matter what). And you become less likely to match the 1400-1500 fps the .357 SIG was designed around.