I think you mean "single action revolver", not "Single Action Only" revolver. That term, just like "Double Action/Single Action" are misnomers in that they are more recently coined terms of action types which have existed for many years. Sorry, just a point to give.
No, a single action revolver, while an incredible fun gun, is not the best choice of a defensive sidearm in today's world. You are limited to six rounds (most of them, anyway), and an action type which is pretty slow for repeat shots (unless your name is Bill Munden). If you are of a mind to carry a revolver, you would be much better served to carry one which is double action. Single actions are great for hunting but when the potential to encounter a BG, or multiple BG's, with semi-auto pistols, you could find yourself in deep kimchi.