Stainless looks silly! For newbies!
I guess I've been a newbie for about forty years now.
I prefer the look of stainless, but I own way more blued (or otherwise black-colored) handguns. The point about black being somewhat more concealable seems valid to me, and there are other pistols that I own that are either not available or at least harder to find in stainless. As a result, about 80% of my pistols are blue.