I'll reply based on a Ruger SA w/ transfer bar and a 1911 w/ firing pin interlock:
The Ruger SA hammer rests against the frame and the transfer bar rises into place only when the hammer is pulled back to the cocked position. So, if you drop it, there is only the inertia of the firing pin to possibly fire the round. As the firing pin is so short, this inertia is very small and this model of SA is considered safe if dropped on its muzzle or hammer. The Ruger SA models before the transfer bar were safe only if an empty chamber was under the hammer. Dropping these on the hammer could easily discharge a round if there was a round under the hammer.
The 1911 has a firing pin interlock that blocks the firing pin from moving forward if dropped on its muzzle. It has a hammer block safety that keeps the hammer from moving if the pistol is dropped on its hammer. The 1911 models without a firing pin interlock have a slight chance of discharge if dropped 4 ft onto the muzzle on concrete, but the same safety if dropped on the hammer.
As you said, "assume the safety is off", I can't understand your question. It is obvious that an uncocked revolver is safer to carry than a SA semi-auto with the hammer cocked and the safety off.
Your example was a DA semi-auto, so perhaps you meant to compare the revolver with the DA semi-auto. For the case of the Beretta M9, I believe it has a rising firing pin block that is activated when the safety is on, so this has been disabled. Chance of AD/ND roughly the same as for a revolver, assuming similar trigger pulls and holster snags, etc. as the cause. The chance of firing when dropped would be higher as you haven't blocked the longer (higher inertia) firing pin because you left the safety off.
Maybe you should compare "apples vs. apples" and ask yourself, "Does a revolver or semi-auto have similar risk of AD/ND if all the safety features are used?"
I believe your question is kind of "apples vs. oranges", which isn't a fair comparison.
I will agree that there is an incredible, unwarranted bias against 1911 carry in Condition 1 as people just don't understand that the hammer is blocked when the safety is on. It isn't some fragile sear/hammer notch that is going to be dislodged when you drop it, or run over it with a truck!
