Well, there are J-frames and then there are J-frames.
- If you want a true pocket gun, the Airweight J-frames in .38 Special +P (models 642, 637, 638, etc.) are very concealable and easy to carry. Much lighter than an SP101. Like
Hastings above, I "love how a j-frame Smith gets forgotten in your pocket due to the light weight and small size."
However, I personally would not use, for defensive purposes, any current S&W with the poorly designed internal lock. (But S&W did a small run recently of 642s
without an internal lock! Snap 'em up.)
- If you want a small .357 Magnum revolver that you can really shoot magnums in, the SP101 is unbeatable. I consider it Ruger's finest revolver. Its competition is the steel frame S&W J-frames like the model 60. They come with the stupid internal lock. The Ruger has no internal lock (so far - act fast!). It is an extremely tough, reliable gun with good shooting ergonomics. Add a Hogue rubber grip and the ergonomics become superb:
http://www.hoguestore.com/index.php?main_page=product_info&cPath=569_2_27_61_398&products_id=3512
Most people find the SP101 a bit too large and heavy for pocket carry. It is a small, easily concealed belt gun. You can load it with .38 shotshells, .38+P comfortable-shooting defensive ammo, .357 JHPs, or even true bruisers like Buffalo Bore's 180 grain hardcast Magnum:
http://www.buffalobore.com/index.php?l=product_detail&p=100
... that'll make your hand smart some, even w/ the Hogues, but I can assure you, the SP101 will digest that ammo and yawn.
Fine general-purpose handgun for the outdoorsman or -woman.