The following information on double-action revolvers vs. automatic pistols comes from Section 46 of Shooting by J. Henry FitzGerald. Shooting is also available to purchase in print.
I have continually spoken of a revolver when police shooting was mentioned and I will here give my reasons. The automatic is fast if the user has by practice become accustomed to its use; still it is almost an impossible accomplishment to instruct a large force and feel that every man can handle the arm safely. The automatic is just as safe as the revolver if properly handled, but if unfamiliar with its use it is not.
It is not as fast for the first shot as the revolver fired double action, for that is one motion to draw and pull the trigger and the bullet is on its way. With the automatic there is the one added motion of pressing down the safety and more time is consumed than with the revolver. If revolver is fired single action there is very little difference in the time of first shot but, after the first shot, the automatic is faster than the revolver for the remaining shots. The automatic is very accurate in fast shooting due to the natural grip and pointing feature as you would point your finger.
The failure to fire through jams in the present-day high-grade automatics of American make may be traced to neglect through failure to keep chamber and barrel clean and free from rust; otherwise, a jam or misfire may be traced to oil-soaked cartridge, which will cause trouble in either revolver or automatic. In Fitz Safety Rules will be found the safe way to handle the automatic.
If an automatic is carried it should, at all times for police work, have a cartridge in the chamber and safety in place because an officer may have but one hand at liberty when the time to shoot arrives and the automatic requires two hands to place the first cartridge in the chamber. The arm should be carried ready for use at all times. I have noted that many departments carry only five cartridges in the revolver. Any revolver with a police positive safety is perfectly safe with six cartridges and that sixth cartridge may save a life.
I am a firm believer in double action with the revolver at short range and, for speed of first shot, the revolver double action is supreme. If I hear from the single-action lovers through this statement it is because they have not put in the days and years of practice with the double-action revolver that they have with their favorite peace maker.