Really it comes down to a few factors IMO.
1-How do you plan to carry? If you plan on using a good holster and belt then you allow for bigger guns and the choices become a bit different.
2-Do you plan to run lots of full house .357 magnum through the gun. Smith and Wesson J frames really are not designed for a steady diet of this. They are not fragile by any means but they really are not meant for round after round of pounding .357, especially the hot 125 grain stuff.
3-Do you want the option of a single action trigger pull? Liability law probably dictates you stick with a good double action only gun, ie no hammer. I however , like having the option of a double action pull. Therefore I usually carry a 638.
4-Do you want 5 for sure, 6 for sure, 7 for sure or 8 for sure. There are guns that hold any of those capacities and all come in models that would work for CCW although the more ammo the thicker/bigger the gun.
For shear bang for your buck it is hard to go wrong with a Smith 642 or 442. They make a butload of 642s so they are cheap, they are double action only, are generally abuse resistent and shoot pretty well. They will have a pretty heavy trigger out of the box though so prepare to shoot or dryfire alot.
Me personally I think that the best CCW gun is the one you will carry all the time you legally can. To me this means ease of grabbing and going and therefore pocket carry. For that reason I think an aluminum framed .38+P revo is the best compromise between caliber, weight, durability, recoil and cost that meets my needs. I don't like those super light, very expensive unobtanium guns and I don't think a bit heavy gun makes alot of sense for an EDC piece. That puts me right in the 642, 442, 637, 638 Smith camp. I have been known to pocket my model 60 as well.
Give me a good 5 shot .38+P and an extra speedstrip or two and I am good to go.
