GunFool:
With single actions, the hammer is cocked when the slide is retracted. So when you load the gun (insert magazine, rack the slide to charge the chamber), you are also automatically cocking the hammer. Then you apply the safety and holster.
The safety does not in any way slow down your first shot. As you draw the gun, when the barrel reaches a 45 degree angle with the ground, you lower the safety. The safety is thus off by the time the gun gets on target. So the safety does not in anyway slow down the first shot. In reality, the short, light trigger on an M1911 makes it much easier to get a fast, accurate shot off than on a gun with a heavy, long-stroke trigger. Yes, you do have to learn to operate the safety properly and to do so without having to think about it.
You are correct that with a DA/SA, you start with the hammer down. You have a long-hard trigger pull for your first shot. When the slide cycles after the first shot, it automatically cocks the hammer. You now have a short, light single-action trigger pull. Before holstering, you must decock using the decocking lever.
Most DA/SA have a decocking lever. Many DA/SA do not have a manual safety -- e.g., Sig. These guns must be carried decocked.
On some DA/SA, the decocking lever is also a safety -- e.g., S&W, Beretta, but this safety can only be applied when the gun has been decocked. These guns must be carried decocked, either safety on or safety off.
Just to confuse things further, the HK USP is DA/SA with an integrated decocker/safety lever and the safety can be applied either cocked or decocked. So the HK USP can be carried either 1) cocked and safety on, 2) decocked and safety off, 3) decocked and safety on.
If you haven't alreay, I strongly recommend that you take an NRA Basic Pistol class. They will provide a semi-auto and revolver during the class, and will teach you the basics of handling semi-autos.
In terms of the safety of the various actions, I often carry a M1911 cocked and locked and feel quite safe doing so. I've also carried DAO guns and felt quite safe using those. I have a DA/SA gun and feel safe using it as well. Any of these actions can be carried safely and any can be mishandled. All require training and practice. I've had a fair bit of training, including training on working from the holster.
The manual of arms for SA and DA/SA pistols is somewhat more complicated than DAO. But either can be learned with proper training and practice.
My preference is for a gun with a consistent trigger pull -- either SA or DAO. I don't like the transition from the long-hard DA trigger pull to the short-easy SA trigger pull of the DA/SA. Personally, it was much easier for me to learn to operate the M1911 safety than it has been to try to master the DA/SA transition. And I find myself better able to get fast and accurate shots with the short, light SA trigger pull. YMMV.
M1911