Ballistics comparison - .38 Super and .357 Sig
Posters above have mentioned the similarity between .38 Super and .357 Sig. Winchester is a company that loads several types of ammo in both of these calibers. I went to the Winchester website and found this:
.38 Super 125 grain Silvertip Hollowpoint - 1240 fps velocity, 427 ft-lbs. energy.
.357 Sig 125 grain USA Jacketed Hollowpoint - 1350 fps velocity, 506 ft-lbs. energy.
So for these common commercial defensive loads, the .38 Super is a "lite" version of .357 Sig, launching a very similar bullet with about 9% less muzzle velocity and about 16% less muzzle energy.
I also looked on Natchez for pricing on practice ammo in these two calibers, and it was similar, with 50 rounds of .38 Super white box going for $14.34, and 50 rounds of .357 Sig white box selling for $15.26.
But one big advantage of .38 Super, to my mind, is that it is available in the 1911 platform, as the original poster mentioned, while the .357 Sig is mainly confined to modern DA/SA semiautos from Sig, Glock and H&K.