.38 Spl and .357 Magnum
Porky6331--One of the nice things about the special-and-magnum combinations (both .38 and .44) is that the specials can be used for low-cost and low-recoil practice, in the magnums.
You load the specials the same for any application, whether intended for use in a .38 or in a .357. You could load the .38's heavier for use in the .357, but then you'd have to carefully label those heavy .38's, and NEVER use 'em in your .38 Special-chambered revolver. Also, the .38 brass is lighter, and its life will be shortened by using the heavier loads.
However (there is always that darn "however!") when using .38's in a .357, remember that there will be a ring of crud deposited in the cylinders at the .38 length, which may make chambering the longer .357's difficult unless cleaned out.
I avoid this by loading all rounds for my .357 magnum pistol, in .357 magnum cases. Most of the rounds are target rounds, for practice and for bullseye league. When I want to slip my hunting rounds into the cylinders, they slide right in.
But if you want to use just the one length of case for reloading for a .38 and a .357, obviously the .38 cases are the way to go.