Lots of thought provoking stuff here, most of it with pretty good background to back up the opinions. Myself, I have a Smith Airweight Ti in 38 Special, and a Cobra derringer in the same. They weigh just about the same, and frankly, I'd rather carry the Smith in any kind of jacket that has extra pockets. In a polar fleece jacket that has a zippered upper sleeve/shoulder pocket on the left arm, the Smith fits perfectly, and as bizzare as it sounds, scarcely prints at all. I think it must be due to the weight/surface area ratio. It stays put in the pocket, and doesn't sag to the bottom, or pull down on the sleeve. You hardly feel it there, and even my fellow observant gun toters have to be told. On the other hand, the Cobra, in the same spot, pulls down like mad, slaps you every time you move your arm quickly, and doesn't stay located. A holster fit to the pocket would undoubtedly help dramatically. In a pants pocket however, the situation reverses. The Smith is just enough thicker through the cylinder that it is less comfortable, and, I think, more obvious than the Cobra, which still moves around more, and pokes you, sometimes less than gently. Again, a holster would undoubtedly help here too.
As for shooting, the Smith will hit anything with aplomb. That gun will shoot just about anything I'm careful enough to aim at within 24 to 30 yards, with just about any ammo I've put through it. It lets you know when you shoot something heavy. The Cobra shoots well, just remarkably high, as has been attested to previously, and sends a fair percentage of different loads through the target sideways at 7 yards. Other loads look fine at 15 yards, so it pays to play. Either gun (3 inch barrel on the Smith) will deafen both the shooter and the target. For serious carry, unless you can't afford anything else, the Cobra is far from ideal, but the mere presence of the gun will repel many. Many more however don't give a rat's pitootee. The recent spate of 380's, not to mention the incredible advances in ammo for same is a far better choice than either from the standpoint of compactness, reloadability, and hide-ability. At least that's how it seems to me. On the other hand $150 or so for the Cobra will, realistically, put alot more of them in pockets than $300- $500+ for either a revolver or a pocket 380, no matter their superiority. Ultimately, any gun you have on you in an emergency is better than nothing, though a war club at close range might well ace any of them if it was already in your hand...
Jamie