Another advantage for guns that have a slide mounted safety/decocker is that they can be safely decocked from the single action firing mode without relying on two-handed, trembling, perhaps slippery fingers to lower the hammer. These guns have a built in hammer block that allows for one-handed de-cocking, either returning it to double action mode or switching it off altogether. We all know of stories of accidental discharges while someone was trying to lower the hammer on a gun with a round in the chamber. At the very least this is embarrassing. The worst cases have happened also.
Frame mounted safeties, such as on the single action semi-auto 1911 style guns, were initially considered essential because of their much lighter triggers than on the double action revolvers they usually replaced. Having one more layer of safety between you and that +/- 4 pound trigger must have seemed like a good idea to John Moses Browning. A manual safety is still a feature on the standard issue military sidearm, the Beretta M9. The lighter trigger pull of most auto-loading pistols are a key reason for having an additional manual safety, just in case a finger ends up in the trigger guard when it should not be there.
The DOWN Side
So, if thumb safeties are such a good idea, how come every gun doesn't have one? One reason is that not everyone gets the kind and amount of training that they should to insure that they do in fact operate the gun reflexively. Just as there are instances where safeties have prevented tragedies, there are incidents where officers have pulled the trigger, but their guns did not fire. Whether it was stress, poor training or some other factor, they simply did not know their gun well enough when it mattered most. They forgot to deactivate the safety. To further complicate matters, some agencies use the slide mounted safeties as de-cockers only, prescribing that the guns be carried off safe and in double action mode in their duty holsters. There is nothing wrong with this, until the safety accidentally gets pushed on without the officer being aware of it. When the pistol is deployed, it should only require a squeeze of the trigger to fire. If the officer doesn't notice that the safety is now on, the gun doesn't fire as needed. Again, the brief seconds, or even fractions of seconds, that it takes to remedy the situation can mean the difference between life and death. This is the main reason that many prefer the simplicity of a no-safety, point-gun-pull-trigger pistol. Of course, if it is that simple for the officer, it is also that simple for someone else who gets their hands on the gun.
Another issue is that many thumb safeties are now designed to be ambidextrous. This makes a lot of sense for agency guns, as they need to be used by both lefties and righties, or when an officer's primary hand is injured. But this puts one of the levers on the out-side of the gun as it is being carried. Brushing against things, as officers tend to do, can activate or deactivate such safeties, leaving the safety in the wrong position. Some people feel this is reason enough to avoid ambidextrous thumb safeties.
Which should you choose? That will depend on the philosophy of the agency, or those individual officers who make the call for themselves. How much training time will you devote to the functioning of the gun? How effective is your handgun retention training? Is there some other reason for selecting a certain pistol and the safety is either there or not, as a part of the package? Another factor that must be considered, whether we like it or not, is cost. Many agencies have moved away from the Berettas and older style Smith and Wessons in favor of less expensive and/or simpler guns, primarily the Glock pistols or the various SIG Sauer models. If that is the case, there are no manual safety options, no further discussion necessary. Many gun gurus advocate that a combat type pistol should be as simple and reliable as possible, with nothing to impede its immediate use. Sort of like, well, the revolvers they replaced. I'm good with that. Just don't pull the trigger, or let anyone else pull the trigger, and things will be fine.
Next month: The Ins and Outs of magazine safeties and grip safeties.