.38 vs .357
Keep in mind that if you're interested in a lightweight or very lightweight snubbie strictly for concealed carry, you may have trouble finding a cost effective firearm in .357 Mag.
I recently purchased a S&W 642 because of the fact that it weighs only 15 oz empty. I wanted a .357, but the only lightweight version of the .357 were made of titanium (Taurus) or scandium (S&W). I think the lightest weighed in at around 12.5 oz or so. The price of the titatnium and scandium snubbies is almost twice that of the aluminum S&W 642. Besides, a .357 out of a 12.5 oz snubbie would be very uncomfortable to shoot. The 15 oz 642 recoil with +P loads is managable, but you wouldn't want to shoot it all day. I can't imagine a .357 self defense round out of one of the very lightweight 12.5 oz snubbies. Ouch.
I have an XD40 service model that I carried for a while, but at 5'-9" and 160 lbs, it was difficult to hide the grip. Absolutely love the pistol, but I found that I had to leave it in the car or at home because it got to feeling heavy and hard to conceal without feeling like I was going to be "noticed". The 642 .38+P fits very VERY nicely in my front pocket with nothing but an Uncle Mikes soft holster to keep the trigger shrouded. Even fits well inside of my suit pants for work. It's lightweight, and actually comfortable to carry. The big plus is that you can have your hand in your pocket (looks like normal hands in pockets) and have your hand on the grip, finger along side the trigger guard (outside the holster), ready to draw very quicky. How many hip mounted or IWB pistols can you do that with without looking suspicious?
I feel confident that at typical confrontation distances for self defense, that a .38+P round or two would be enough to put a stop to the life threatening situation.