I think the primary requirement for a Personal Defense handgun are as follows, in order of importance.
1) It should be totally reliable.
2) It should have sufficient power to provide an acceptable level of defense. As we have all seen from reading the various stories on the net, with any handgun a true "one shot stop" is not assured but a more powerful caliber does trump a weaker caliber to some degree. IMO any cartridge that delivers a minimum of 350 ft.lbs. at the muzzle is a minimum requirement, any less and you should be shooting for the head.
3) It should be enjoyable to practice with enough that you can become exceptionally profficient shooting it. In addition, it should be a weapon that you can control well enough to achieve a 1/2 second interval time with while getting good strikes on target. My personal criteria for that is to be able to hit a 4 inch target at 25 feet with every single round fired at this rate.
4) It should be light enough to carry all day and easy to conceal in a variety of manner of dress.
When all 4 of these factors are taken together, the best choice for me wasn't a revolver, it was a semi-auto. Specifically, a 40 caliber Sig Sauer P239. In 1000 rounds downrange it's been perfectly flawless. The 40 S&W has a decent reputation for stopping power and performance. The gun fits my hand so well that it's sometimes a bit scary how well I can shoot it and I have no problem controlling the muzzle flip. It's 30 ounces and while that may sound heavy it's not a burden in a good holster. In addition it's very easy to make disappear.
Now, contrast that with another favorite gun, my S&W model 620. Like the P239, it's been totally reliable. Loaded with 357 Magnums it certainly has more than adequate power and loaded with good HP ammo, overpenetration shouldn't be a huge concern. However, loaded with JSP or LRN overpenetration could be a concern. Criteria number 3 is where I have a problem with the 620. With full power Magnum loads I cannot control it well enough to meet my criteria when trying to maintain a 1/2 second interval. At 40 feet, on my best days I've only been able to manage a 6 inch grouping at this firing rate. With my P239 I can group as tight as 2.5 inches at this distance on a good day. Granted, I can load it with 38 +P and shoot tight enough but it's then below my minumum threshold for power. Finally, while it's concealable with some types of dress, it's too large to conceal well under a T shirt. In addition, it's a bit heavy for all day carry.
Yeah, I know about the J frame and how easy they are to conceal. The problem with the J frame is that for commercial ammo your faced with only 3 choices in caliber. The 38 spl. which I feel is not powerful enough even with a 3 inch barrel, the 38 +P which has a bit more power but still lacking, and the 357 Magnum which IMO is just too powerful for any gun under 35 ounces in weight. With most of the 357 J frames your basically limited to just 1 shot, after which you'll be shaking your hand trying to get some feeling back in it. IMO, what's needed to make the J frame practical is a cartidge similar to a 9mm +P or 40 S&W. In a 26 to 30 ounce gun, a 350-400 ft.lbs. energy load would not only be managable, it would also provide an adequate level of power. As for the Scandium and Aluminum J fames, they are just too damn light.
