I'm of the opinion that an enclosed hammer snubnose revolver is one of the best choices that a Civilian can pick for a PDW/Personal Defense Weapon. Note that I said Civilians and not Law Enforcement or Military Personnel as their "job description" differs greatly from that of the lawfully armed Citizen interested only in self-preservation.
The first advantage that an enclosed hammer revolver brings to the table is SIMPLICITY of use.There are no external safeties to manipulate or decocking levers to fool with.There are no magazines to contend with and it's use is straightforward. Point and pull the trigger is about all there is to it. Dexterity degrades greatly when people are under great stress and if something is overly complex or that person is not trained to the point where skilled movements are reflex, you can expect less than satisfactory performance and results.The snubby Revolver is a natural "point shooting"weapon as well as being fired one handed,which is a common reactive method in an actual defense shooting.
SAFETY is the second factor that gives a DAO(Double action only) revolver an advantage over semi-automatics for use by those not highly skilled or trained with firearms. The long and heavy trigger pull of the DAO protects against accidental discharges,which are a real possibility when the adrenaline is flowing and your life or the lives of those you love is threatened.The trigger pull on most semi-automatic is usually greatly lighter as well as much shorter.
The snubnose is also about SPEED since it is about the fastest gun to bring into play with it's short barrel. Drawing from concealment it is much easier and faster to clear the holster or pocket with a gun that has a short barrel vs one with a longer one.You can also acquire targets quicker since arced movements will be faster than with a longer barreled gun.The smooth profile and rounded shape of the hammerless revolver provides a snag free draw from CONCEALMENT. It's real easy to slip a snubby Revolver in your pocket to answer the door or go out and get the mail etc. A hammerless revolver is also the only gun that can fired repeatedly from a coat pocket or entangled in a bath robe,bed blanket or whatever other mess you might encounter in a real world defense situation.A semi-auto MIGHT give you ONE shot from inside a pocket although pushing the slide "out-of-battery"(slide slightly pushed back when pull the trigger causing gun to malfunction) is a real possibility and the gun will would likely jam/entangle even if you did manage a first shot making any follow up shots immediately impossible.
The snubnose revolver is also the hardest handgun to take away from it rightful owner.The ability to maintain control of your weapon is called WEAPON RETENTION and it is very common for the bad guys to try and disarm the good guys. This is especially true when it is a Woman that is holding Her assailant/potential rapist/robber at gunpoint. Real World altercations happen at very close distances and tend to blow up in your face unexpectedly, so it's very likely that you'll find yourself nose to nose with your attacker and with it's short barrel and rounded shape, the snubnose revolver gives the attacker very little to grab onto and will usually fire even if they do grab it which is generally untrue of the semi-auto. Larger "combat grips" such as the ones pictured on my S&W 640 accentuate weapon retention even further although they do make the weapon less concealable.
Revolvers also tend to be more RELIABLE than semi-autos although many will dispute that.If a Revolver malfunctions/Fails to Fire, all that is usually required is another pull of the trigger. A jammed/malfunctioning semi-auto is much more difficult and time consuming to clear, especially when the chips are down and your life hangs in the balance. An auto needs a relatively firm/stable platform fro the slide to cycle against. In a defense situation, you usually don't take a orthodox shooting stance and may even have to or instinctively fire one handed, so limp writing causing the autoloader to jam is real possibility especially with people who may lack hand/wrist strength(i.e. Women & smaller stature Men). A Revolver is much more tolerant of less than ideal cleaning and maintenance as well as less finicky about ammunition used than a autoloader.Under/Over Powered Ammo may not cycle reliably in an auto.You can also load a Revolver and stick it in a drawer and be pretty confident that you can pull it out even years latter and expect it to work. A Revolver is essentially "at rest" at all times unlike a chambered/loaded semi-auto whose springs are under constant tension.
Revolvers tend to be chambered in more potent calibers than equivalent sized autoloaders.Perhaps partly due to the full chamber/case support offered by the Revolver, but also because it's very difficult to design a reliable auto-loader in a very small package such as the tiny .380 ACP's from Kahr and Ruger which have been shown to be less reliable out-of-box compared to the larger framed guns.The same holds for the micro 9mm guns with perhaps the exception of the Glock 26 although it isn't really all that tiny or light.This simply is not true with small revolvers as they've proved to be just as reliable as their full sized counterparts.Autoloaders ultimate top end power is somewhat limited by not only chamber support,but also by required spring strength. Once you get past a certain power point,the springs on the gun will have to be so strong that it will be difficult to even rack the slide on a autoloader if the standard recoil operated design is used. That's why you just don't see many auto's in Magnum or other very powerful calibers(The Desert Eagle is a different design,gas operated,not recoil). I'll take a .38 special +P/.357 Magnum over a .380 ACP any day.The snubnose Revolver is NOT a target gun, but it doesn't need to be since self-defense shootings occur at very close distances.Most laws mandate that if you can avoid a situation,then it is your responsible to do so and only allow you to use deadly force if there is absolutely no other recourse. So, that means if the bad guy is 25-50 yards away, you probably could escape/retreat , so shooting him would be unjustified use of deadly force and you would find yourself on the wrong side of the law if you did so. Nor would the snubnose Revolver be the ideal gun to have in Military firefight or a Police stand-off, but the dynamics of those situations differ greatly from the average Citizens needs.The semi-auto's greatest advantage lies in it's capacity/number of rounds it holds.Most Revolvers usually hold only 5 or 6 rounds and are slow in comparison to autos to reload(although speedloaders and speedstrips do narrow the speed gap,but you must train/practice with them to become proficient and people like Jerry Miculek can reload his Revolver faster than most can their semi-auto http://www.snubnose.info/docs/Theory.htm (scroll down to video"Miculek Shooting"). But, statistics show that most CIVILIAN defensive uses of fires are resolved in 3 Rounds or under. That's why more often than not, my go to/always available first line of defense is a snubby revolver for all the reasons I listed even though I do often have a high capacity Glock or other semi-auto close by for the extra firepower, but I don't think it irrational to simply play the odds and go solely with the snubnose revolver as the odds are definitely in your favor and the snub is more than capable of resolving the vast majority of situations that I or Joe Blow is likely to encounter in our everyday life and if that's the only gun.
People often make firearm decisions largely based on what the Police or Military use, which is understandable and could be reasonably considered at least to some degree and in the proper context. But, remember the differences in duty, goals and scenarios that separate Civilian defense and the job of sworn Law Officer's or Military Personnel, so that you don't use their picks as the sole basis for your choice of personal defense weapons.