Under stress, with adrenaline roaring through the bloodstream, folks make a lot of mistakes, even when trained. Police routinely hit ~10% of fired shots in a officer-involved shootings. Adding a safety doubles the complexity of the mechanical motions required and doubles the probability of an error. That is why I prefer DA/SA hammer down (CZ 75), since there is less to think about, and the first shot is less likely to be inadvertent. Unfortunately, there are no subcompact DA/DA single-stack pistols, so I carry a 9mm Shield and am very careful with the trigger.