Sorry to be so late to jump in... I just saw the post a couple of minutes ago... (been spending nearly all my time in the S&W forum).
http://www.smith-wessonforum.com/
Anyway... I think the question has been well answered. But I will offer my viewpoint on the J's, K's, L's and Rugers.
My J-frames include an early model 60 and a more recent 642. Personally, the only configuration of a J that really makes sense to me are the models with sealed, internal hammers. These guns are belly/pocket guns and little more. The gun to take when you can't take anything bigger. Of them all, I would speculate that most experienced belly-gun guns might single out the 642 as about the ideal pocket J-frame. The larger and heavier 640 is a great gun and the only other J-frame that makes sense to me.
Given the choice, I would take a K-frame (13, 65, 19, 66) over any J-frame in a heartbeat for feel, controllability, capacity, comfort, accuracy, and trigger.
BUT, there are times when the size of a K prohibits me from packing, in which case I slip my 642 into a front jeans pocket or coat pocket. This light, little gun is amazing in terms of how easy it is to have with you, comfortably. And since it's hammer is completely sealed inside the butter-smooth lines of the gun, you can even hold the gun in your hand ready to shoot while inside a coat pocket - comforting when walking through high-risk areas without revealing that you are armed and can fire instantly, even through a coat pocket if absolutely necessary.
Shrouded hammer models are a decent second choice for a pocket gun, but the open top of the hammer shroud allows dirt, lint, etc. to settle down in the gun and can be a little bit of a pain to clean out...just not as elegant as the internal hammer models.
Remember, though, that the 642 is a gun which is great to carry, but kinda sucks to shoot with (as compared to K's or other larger guns). It's a gun to have if you need it and hope you don't have to shoot it. It may surprise a new owner to find how difficult it is to shoot such a gun quickly and accurately double action (any defense situation will require double action shooting; cocking the hammer just aint gonna happen!)... much practice is needed to really hit well beyond just a few feet! Part of that is due to the relatively heavy double action pull, made less sweet by the coil-design vs. the leaf-design hammer spring in all the larger Smith & Wessons. This is a gun, however, that there is no excuse not to have with you no matter how light you dress.
If you can wear an inner waistband holster (IWB), then I would step up to a 640 which is a bit larger and a fair bit heavier, but more comfortable shoot. It's still just a J-frame, though, holding 5-rounds. The Ruger SP-101 is in the same league as the 640. I have an SP-101 3" and it's a great gun. Both the SP's and the 640 are great guns, but neither quite as concealable or comfortable to carry as the 642.
For the most part, a concealed carry revolver is at it's best with an internal hammer or a bobbed hammer and fixed sights. This makes producing the gun from concealment very slick and snag-free. And in a typical defense scenario, there's no need for hammer spurs or adjustable sights.
The next step up would be the S&W K-frames: 13/19/65/66, etc. (Ruger offers no guns in this size category as the Ruger GP line is a bit larger and comparable in size to S&W's L-frame guns, the 581/586/681/686 etc.)
Sadly, S&W offers little in the way of K-frame .357 models anymore... at present just the LadySmith, as far as I know. If you want a 13/19/65/66, look to the used market. For a defense revolver, these guns are really in the sweet spot for size, weight, power, feel, accuracy. There is no trigger quite like the trigger in a S&W and it's surprising how accurate these guns are with the fixed sights.
Smith & Wesson Model 65-5 .357 Magnum 3" barrel
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Smith & Wesson Model 13-3 .357 Magnum 3" barrel
Of course for hunting or serious target competiton, you would choose larger guns with adjustable sights.
As I've said elsewhere, my most favorite revolvers are those with fixed sights and 3" barrels. Among models that meet this criteria are Rugers wonderful GP-100. I happen to have a blue steel and a stainless steel GP-100 with 3" barrel and fixed sights. These guns are about the same size and weight as a S&W L-frame. Here's my stainless model... and it's a fantastic carry/nightstand/home/car/RV defense gun... superb. The GP line is very comfortable to shoot potent .357 rounds with and will stand up to heavy loads quite well indeed.
Ruger GP-100 3" Barrel, Fixed sights, .357 magnum (KGPF-331)
I will soon acquire a fairly rare S&W, a model 686 CS-1. It's a 686 with 3" barrel and round butt issued to the US Customs Service. When the Custom Service "upgraded" to bottom feeders, these sweet revolvers came onto the used market. Can't wait to pick mine up!
Another project of mine is a S&W 681 4" (basically a 686 with fixed sights). I've found a new 3" 686 barrel at the S&W Performance Center which they will install on my 681 to make a 3" 681. I will then converted the square butt to round butt... this will make a very, very sweet defense revolver indeed.
I offer nothing about Taurus because I have no interest nor knowledge in them. From what I've read, they make good quality, lower priced guns these days, though probably not quite in the league with S&W and Ruger. I'm sure Taurus guns will do the job very well indeed, but they just don't appeal to me.
Personally I can find everything I desire in used S&W and new/used Ruger guns. I buy only used S&W guns because I just don't like the internal locks in the new ones, though the new ones are great guns. And you can expect Rugers to have such locks on all their guns in the not too distant future.
Be safe, shoot often and well, enjoy!
