Alright, here is a hypothetical:
Let's say you've been hired by a large metropolitan Police Department with a high crime rate and you are encouraged to supply your own sidearm (true story). Long story short, they'll permit to you carry a high-end Kimber 1911 .45ACP or a Sig-Sauer P220R .45ACP.
Here is why I would choose the double action SIG P220 over a single action SIG P220 and the 1911: grip and thumb safeties!
The real problem isn't either gun's performance. Both are fine, provided the user is satisfied with reliability, ergonomics, grips, sights, trigger weight, etc. The real issue is the nature of the fighting that the police officers typically get involved in. Encounters tend to be very close with a high probability of physical contact (not including cuffing) between the officer and suspect.
What I have learned is that the MARTIAL ART of SELF-DEFENSE is MORE important tha the gear. This sort of conflict REQUIRES proficiency in hand to hand, knife and gun. It is EXCEPTIONALLY easy for someone to interfere with the drawing of a firearm and/or close the short distance before the weapon's muzzle is on target.
This is the result of a FAILURE in TIMING on the part of the good guy:
Fighting for the gun mistakenly introduced at the wrong time
Notice how the bad guy (on top) is working to control the right arm of the good guy. A gun has been introduced into the fight and is now available to the bad guy if he can manage it. There are times to draw and times to use a fist; this good guy misjudged the tactical situation and now gets to fight for his weapon. Fortunately, retention issues can be solved with Level 3-5 retention holsters such as made by Safariland.
Any gun with a safety is a liability in this situation because of physical pressure. If the good guy cannot get a solid grip on his weapon (and that definitely happened to me in these non-cooperative exercises), the gun is temporarily disabled. This is a BIG problem because THE SHOT MUST GO OFF NOW and the good guy may not get another clean shot. Jams are very easy to induce, even with just pressure of an elbow against the slide. Grappling over a weapon is at best a bad situation; the good guy better know his physical ground game and be physically up to the challenge.
Some folks will claim that the 1911's safeties will prevent the bad guy from operating the weapon. Relying upon a "what if" like that is not prudent and is a denial of reality. We cannot presume to know the skill sets of the criminal in advance. One case in point: gang members getting into the military, getting deployed to Iraq, and then returning to the US to use their skills and experience. Prepare for the worst because your adversary may actually be a better fighter!
Force on force exercises such as the one above demonstrate the problems that can occur with shooters put under pressure. They fail to sweep their safeties or mess up achieving a solid grip (sometimes with help). The result is that they take fire. Fortunately, movement is a great defense, but it lasts only so long before the adversary requires a sight picture. These problems occur for folks with extensive experience with 1911's and similar guns. It's a mistake that can happen at any time and with a little bit of help (like a punch to the hand or gun arm), the probability of failure to disengage the safety goes up.
Our ancestors knew what they were doing when they invented the double action revolver. Go read Ed McGivern's
Fast and Fancy Revolver Shooting for a detailed look at the controversy of the 1920's and 1930's surrounding this issue.
