Chambered and Safed
Sorry about this long post!
My favorite carry is a Beretta cougar in 9mm, essentially a slightly smaller Model 92. Chambered and safed. The thumb safety pops off easily as the gun comes up, leaving a long heavy double action trigger pull to fire the first round. i carry it this way for several reasons. I can't be as expressive as some of the prior posts, and i'm not as well trained or knowledgeable about such things, but let me try to explain my thinking.
First, the chambered round. I hope i never need to draw on a human being. Ever. But if i do, the gun needs to be ready. Racking the slide takes too much time, too much movement, and makes too much noise. With a steep ramp and a short 9mm round, if you try to baby the slide (as in, let me very quietly chamber a round so the BG won't hear it), the round can easily jam halfway out of the mag. Not happening.
Second, the safety. On the Beretta, the safety rotates the firing pin (or striker, whatever it's called) 90 degrees and de-cocks the hammer. The gun is out of battery. ADs are essentially impossible unless the safety comes off or malfunctions. Yet it takes only a little effort and no extra time to flip it off with my thumb as the gun comes up and away from my body. Also, if the gun is ever taken away from me - as Toronto explains, yes it can happen - the extra split second the BG needs to figure out the safety is a margin i want. Also also, if the BG tries to rack the slide at that point, likelyhood of a jam is increased as it has to first eject a live round. If he closes the slide by hand (like you see on TV all the time) rather than lets the return spring do it, likelihood of a jam is increased yet again. Another potential margin for me.
Third, the holster. I carry IWB. Until i pickup a micro pistol like the LCP, pocket or ankle carry is out. I have an Uncle Mikes IWB, reversible for either side carry. The trigger housing is completely covered. The butt stays right on my belt - never prints but is very accessible. I'm left handed, so i carry at 8:30 or 9:00.
Fourth - i practice the draw/flip safety off move regularly. I completely unload the gun. I insert an empty magazine, and one snap cap in the chamber. I check it again. Then in the privacy of my office or my garage, pointed in a safe direction, i'll practice the draw. Slowly. Why slowly? because when you need to be fast, first you have to be smooth. Once you're smooth, you can go faster. One other move i practice - I turn some to my left, reaching for my wallet (like i'm complying with a mugger) but instead making the draw. Most times i don't pull the trigger, just draw, unsafe and present. I do not want to ingrain that in my memory so that i end up shooting instinctively when i might not have to. Other times i do. It depends on the scenario i am drilling myself for. But considering that handguns are used to stop crimes millions of times every year without a shot being fired, i practice that way most of the time and trust myself to know when the situation calls for immediate fire.
Personally, i carried unchambered for a couple of months. Then i got better informed, more comfortable with my carry gun, and after a lot of practice, decided that the chamber needed to be occupied. If nothing else, it adds to the magazine capacity. You never know if that one extra round might determine whether you or someone you care about lives or dies. Isn't that why we carry?