The consensus among serious handgun users is that the shooter should be trained for the gun platform that he is going to use. Thus a 1911 shooter needs to learn to use the thumb safety, and to carry the pistol "locked and cocked" as it was designed.

The M&P cannot be carried cocked and locked, and there are 3 safeties on the gun already. The M&P will not fire unless the trigger is pulled---like a revolver. The add-on thumb safety is available purely to satisfy political requirements imposed on police, and has nothing to do with actual firearm safety.

It is much like requiring an extra safety on a revolver to prevent pulling the trigger, which relates to import restrictions now.

IMHO, the thumb safety on an M&P is a mechanical device that attempts to compensate for poor training. The only way to eliminate the need for proper training is to totally disable the gun so it can never be fired....which is absurd on its face, isn't it?