I'd go with the Smith 640. For years, back in the day, a Smith Model 60 with bobbed hammer was my primary U/C piece. Second choice would be the other Smith.
I currently have a Ruger LCP as my "always" gun, as it fits unobtrusively in a wallet holster, but I'd opt for the old 60 if I couldn't carry chamber loaded.
Violence is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and valorous feeling which believes that nothing is worth violence is much worse. Those who have nothing for which they are willing to fight; nothing they care about more than their own personal safety; are miserable creatures who have no chance of being free, unless made and kept so by the exertions of those better than themselves. Gary L. Griffiths, Chief Instructor, Advanced Force Tactics, Inc. (Paraphrasing John Stuart Mill)