http://www.greent.com/40Page/ammo/357/357SIG-advoc.htm
Great link to .357sig info.
.357sig (3.9" bbl)
Cartridge Penetration Velocity Energy 25m Accuracy
Corbon 115 gr jhp 12.5 1450 537
Federal 125 gr jhp 13.7 1418 548 2.13
Corbon 124 gr HP 16.5 1400 540
Federal 125 gr FMJ 17.5 1394 536 2.25
Speer 125 gr GD 14.5 1374 520 2.00
Speer 125 gr TMJ 17.0 1355 505 2.13
Reming 125 gr jhp 14.0 1339 485 2.38
Hornady 124 gr XTP 13.5 1306 460 1.88
Hornady 147 gr XTP 13.7 1218 480 2.13
Federal 150 gr jhp 13.25 1127 422 2.50
Here's specs on a typical .40 SW (4" bbl)
155gr GDHP 1200 fps 496 ft-lbs
Seems the .357 will have (typically) slightly more energy, with slightly less momentum, and slightly less recoil.