I voted for the 637, as thats the one on the list I have, and the only one on the list I've fired.Fun and challenging gun to shoot, and GREAT for CCW.I also got it specifically because it DOES have an external hammer, as opposed to the 642.I can certainly understand why most people would prefer no hammer, bobbed hammer, or shrouded for ccw, but I just dont like the looks of a revolver with no hammer, and the hammer has NEVER been a problem for me in regards to snags or anything, even with pocket carry, so.....
I just think the snubbie with hammer is very "classy" looking (but if I really thought it would ever be a snag/safety issue, i'd carry something else, but still have this on just for the looks of it.