Although the Glock (and its emulative systems) tend to be the dominant pistol in the market, I am aware that not everyone selects or prefers it. I recently had a consulting contract where the shooters were using the SIG P226 (don't ask). To prepare I brought out some old DAs I had in the safe and began working with them. Nothing had changed.

My first police semi-auto was a SIG P-226 way back in 1988. I shot Distinguished Expert with it and carried it for years. Later when the 3rd generation S&W was selected by the agency I worked with, I used that. It was like a rough Beretta 92. I took that weapon to Gunsite in 1990 and not only shot the top score in the class but won the shoot off against an entire relay of LAPD SWAT with their 1911s and several LAPD HITS instructors with their 92Fs. One could say I know a few things about the trigger system.

We will be examining the DA concept to answer the needs of those who use it, and prefer it. And no...I am not going to sell all my Glocks. You are the weapon...your pistol is only a tool. And nobody says you can't have several tools.

Advantages and Disadvantages of the Double Action Pistol:

The Double Action pistol's trigger is its heart and both an advantage and to some, perceived as a disadvantage.

1).  HOLSTERLESS CARRY:  It allows for holsterless carry in situations where a holster may be contraindicated (such as a place where it might be socially unacceptable to carry a weapon, but tactically necessary to do so). Why is holsterless carry important at such times?  Those of you who have carried in those places will know that there are times when you may need to divest yourself of your weapons preemptively, such as when you are about to be searched, or when about to be contacted by an authority figure.  An empty holster, once discovered, will get you unwanted attention.  Whereas a found pistol may be easily discounted if it is not on your person. Yes...this is more for the "dark arts" - undercover type guys than the "good citizen" types, but there it is.  Holsterless carry.

2).  GREATER SAFETY UNDER DURESS:  The inherent safety of the long trigger allows for leaving the weapon in situ, on a nightstand or desk, without concern. And if grabbing up that DA pistol in the middle of the night to answer that "bump" in a sleepy stupor, a wandering trigger finger would not potentially betray your intentions like a short/light striker type trigger might. Never say never.

3).  AMAZING SINGLE ACTION TRIGGER:  While trouble with the long-and-heavy double action trigger may be mitigated by training and by technical means, the polished and tuned single action trigger on these can be made amazingly crisp and light making the accurate shot easier. Such SA triggers are often better than what is safely possible with a striker fired pistol, and comparable with a "street" 1911 trigger. In fact, the tuned and light SA trigger on a properly arranged SIG P-226 would be considered completely unsafe on a Glock.

Now I am discussing the triggers seen on the traditional Double Action systems.  A Glock and a SIG P-320 are not DA pistols regardless of that the parrot in the factory sales shirt tells you.  They are in essence striker fired single action pistols if we muct categorize them, but they are not what we are discussing here.

And the various DAO (double action a magazine fed revolver), and DAK and various other variations that seek to eliminate the single action portion of the trigger are poor choices for any over achiever.  Their sole purpose in design, execution, and marketing is to allay the fears of the non-dedicated personnel who will be issued them and the poor administrators that must manage such people. 

Some will tell you that they are good choices for "threat management", and "police duties".  Nonsense I say.  My way of "managing a threat" is to be able to kill it surgically and quickly...not have a debate about the importance of my "threat's" life while I have to contend with a long drawn out trigger press.   That they can be used well with practice does not remove the fact that they force the user to start way behind the starting line.  I would avoid them if possible.