While the responsibility for an AD will ultimately be on the the user, it is much easier to have an AD with a SA gun.
This is a debatable point.
There is plenty of documentation to back this up. A major reason you won't see very many SA handguns allowed in the miliary or LE.
The transition to da/sa pistols and away from sa pistols began before the Second World War and continued after it. The main reason had to do with training large numbers of men in a short period of time. Armies found that it was safer to do so with da/sa guns.
Law enforcement basically found the same thing. To arm a good many people who were not particularly interested in guns but were required to carry one and train them in safe gun handling they found that a da/sa gun worked best. They did not have the money for additional training.
Statistics are unclear whether it helped cut down on ads or not. This is because with the transition to semis, cops at least, tended to shoot more.
If the gun is mishandled it is easy to have an unintended discharge irregardless of the type of trigger. But for the untrained some type guns may be easier to set off when the person holding it don't want it to.