What R.W. Dale said makes more sense than what I'm about to say, but I'd buy a .38. The little 5 shots are not easy on your head, hands or ears in .357. Lots of blast that's hard to recover from for the follow up shots.
I'm constantly looking for a like-new Colt .38. 6 shot, classic style. Remember the 2 1/2" Diamondback with adjustable sights? That was my idea of a nearly perfect carry gun. The Detective Specials were very nice also, and good enough for plain clothes cops at that time. The .38Spl. is as effective as it ever was, even more so with modern ammo. Back before cops went to autos, my issued gun was a 2" Model 10. Bulky for a .38, but I was mighty pleased with it, especially at the range. Issued ammo was the Federal semi-wadcutter 158 in non +P. Then we went to hollow points, then later to 158 hollow point +P. I loved 'em all.
Then the "wonder nine" came out and everybody wanted one. Almost same ballistics as the .38, but many more rounds. Then we changed to the big Smith and Wesson 10MM with sub-sonic ammo, just like the FBI. Guns wouldn't work with the lower powered rounds. Next was the .357 Sig, which is still the current issue. I would have rather kept that Model 10.
It can be argued that the .38 has not kept up with the times, and that they were so popular then because not much else was available. If your firepower in a gunfight was a .38 Spl, you were probably facing nothing bigger. All that throws favor on the .357M. I suppose that's one of the few good things about getting old. One can look back at the older guns that had real class and were made out of real blued steel. Not that plastic and scandium/titanium isn't better, it just doesn't have the same romance of the Colts or the older Smiths. Romance won't save your hide, so I'd advise anyone shopping for a .38 vs. a .357 to think about the pros and cons of each. But for me, make mine a .38 please, and hold the technology.