The .357 SIG is a .40 S&W necked down to .355� to try to get .357 mag revolver velocities in a 125 gr. bullet. For the most part, they probably succeed.
The 10mm is a straight walled case that uses a .400� bullet to velocities somewhat below the .41 mag. The full power 175 gr. 10mm Win Silvertip is about the same as the somewhat attenuated .41 mag 175 gr. Silvertip.
The .357 SIG is a high speed light bullet. The 10mm is a bigger, heavier but slower bullet. The cartridge is also longer at .45 ACP length where the .357 SIG is 9mm length, so the grip of the guns in 10mm is longer for and aft, basically the same size as the .45 ACP.
