My Thoughts for what they're worth
My carry guns are mostly DAO.
DA/SA Pistols:
While Double Action/Single Action pistols are generally great, there is one thing that has always bothered me about them. Your first shot, often the most important, has a different trigger pull, in both length and weight. Also, most people tend to train most with these weapons in Single Action. They build up great form and muscle memory to the single action trigger, then throw the first round in a threat situation.
-- If your an exception to this, great. I do have a DA/SA handgun, and I intentionally reset the hammer between sets in an attempt to train for the varied trigger. I still have more spread in a double tap with a DA/SA than a DAO
SA Pistols:
Single action pistols are great for target shooting, a light, short, crisp trigger pull really helps accuracy, but walking around cocked and locked means putting absolute faith in a mechanical safety, and training to drop the safety during a draw.
The later you have control over, Practice, Practice, Practice. The second you have some control over (quality parts, careful maintain, routine replacement of worn parts prior to failure) but I'm an engineer. Mechanical systems can and do fail. I do still, however, occationally carry a cocked and locked Single Action pistol. I'm more concious of carrying it than I am my DAO pistols.
DAO Revolver:
I have one of these as well. The internal hammer design reduces snag points, but the 9lbs trigger is smooth, but both long and heavy. One good thing about the trigger, it builds up finger strength and endurance and slows rate of fire, which is useful when you only have 5 rounds per reload.
SA Revolver:
The only one I know currently is a blackpowder pistol. I wouldn't carry it for self-defense unless I had no other options (like the fact that you don't need a pistol permit in NH to carry a patch & ball revolver concealled)
While these are the classic "carry" guns of the 1800s, even if I had a SAA (would love to) I wouldn't carry it for self defense. Having to draw the hammer back just slows things down too much in an emergency.
DA/SA Revolver:
I have one of these too. It's too big for comfortable concealled carry. It's for hunting and target shooting. The DA trigger is around 11lbs and rarely used. The single action trigger is in the 3lbs range and much nicer. In an emergency, most people are going to use one of these pistols as a DAO pistol because they're not going to work the hammer between each shot, and if they do pull that hammer back as they draw (like a single action revolver) they again have a gun that has a different trigger pull on the first shot, though at least that single action trigger is lighter and likely what they practice with the most at the range, so hopefully it's the most accurate.
Now, with DAO pistols, every squeeze of the trigger is exactly the same, even if not the best, its consistant. That helps you develop better muscle memory for better aim in a stressful situation. The safety is typically built into a long, heavy trigger pull, but it's one you have much more control over and a little less to worry about than a cocked and locked single action.
I've used 3 different styles of DAO pistols as well:
Single Strike DAO pistols (like Glocks) have a medium trigger length and weight, but rely on a partially cockec firing pin. If the firing pin is released, the trigger alone can't cycle the action, the slide must be cycled to reset the striker.
Multi Strike DAO pistols (like NAA Guardians) have a much heavier trigger pull as the trigger cycles the firing mechanism completely, allowing the user to pull the trigger and attempt a second primer strike on a failure to fire without racking the slide.
Re-Strike DAO pistols (I don't remember which model had this, but I've used at least on) normally function from a partially cocked firing mechanism and share a medium weight trigger pull with single strike DOA pistols, however in the case of a failure to fire, the trigger can engage the firing mechanism from it's fired position and reset it. This increases both length and weight of the trigger pull, but allows a restrike on a failure to fire, where single strike DAO pistols do not.
Are they great target pistols? No, but they can hit a pie-plate at 7 yards, which is the goal of a self-defense carry pistol.