I would go with the ruger sp101 or possibly a S&W model 10/ or other k frame snubby or steel j-frame(model 36 ets.), I take it you wanted the short barrel for the close (doorway-style) range at which you will engage someone. The 642 is a good choice for carry but since you aren't going to pocket carry why opt. for the alloy frame? Why restrict yourself to a harder-to-shoot alloy frame gun, grab a revolver with a little more heft and a little better(bigger) grip. This will help you get a more accurate and faster follow shots. I personally just don't see any reason to go for the airweight when a heavier revolver will be easier to shoot and work just as well for the shoot range answer-the-door mission. Just my humble opinion by the way.