This is fun to think about. However, I don't have a license since I live in a pretty safe area (I live near Washington, D.C.) and my personal experiences have not suggested it would be useful to be armed very often. Or as Jeff Cooper said, "I don't go in places like that."
But seriously, there are so many situations and so many choices. The requirement to pick only one handgun (revolver or pistol) is a realistic one both for reasons of economy and also because when you go somewhere, you would usually only take one gun.
My wish gun is a .38 super Government model. My wish second gun (I know--you didn't ask that) is a .380 Government model. Guess what: I like Colts and they both work the same way and both are hard to find. I've owned more than one of each, too.
My idea of a more practical revolver is a 3" S&W M13 or variation thereof, even in .38 special. This isn't a hunting situation and even a .38 special will handle anything around here at arms length transactions. For a .357 I'm happy with the light bullet loads. Terrific blast but recoil isn't so bad.
But since I said I like Colts and I'm very much a traditionalist, I might even pick a Colt Police Positive Special and they are really hard to find.
Funny, I don't have a single one of any of those at the moment, though I've have at least two of each at one time or another. So what do I have now? A Star BM and a 4" S&W M13.
I don't think the ammunition matters as much as all that given other, more important problems, such as carrying the weapon concealed day in and day out, and, should the time to use it ever arise, actually drawing the gun and hitting the target in time to prevent whatever I needed to shoot to prevent. Generally, the latter problems seem to be just assumed away in most discussions.
My wish list could go on, by the way.