Hey, you picked my two favorite calibers, congratulations.
I love my Dan Wesson Bobtail 1911 .45, and I also love my 2" Ruger SP101 with a spurless hammer. I also carry a 4" XD-40, and it's fine, but I don't love it.
I've never been able to convince myself to carry a 9mm or .380. I had a .32 as a pocket gun once, but I hated it.
I carry my 1911 or XD all the time, and I'd like to get a crossdraw holster for the SP101 just to see if I like it that way.
If you're looking for something small, you might take a look at an SP101. Apparently they're a little heavy for a .357 snub, but I can't tell when it's on my belt. I'm sure there's a good S&W you could go with too, but I'm a fan of Ruger. If I had to pick a plastic gun, I'd be taking a good look at a Glock 30 or 36. They seem like they'd tuck under a shirt pretty well.
Personally, after carrying my 1911, I don't think I will ever be happy carrying any other style pistol. There's just something about that design that I love. But there's something about revolvers that I like too, which is why I'm going to do both.