Assuming the S will hit the F rapidly and without warning and the episode will be over in 2-3 seconds, it doesn't matter to me if the firearm has a cylinder or a slide, it just has to meet these requirements:
1. It has to hit where I'm looking without aiming. Yes, aiming is much better, but in sudden death I want something that fits my hand such that it will hit where my bug-eyed eyes are staring just by point shooting it. I missed a very pissed off Florida razorback three shots out of four at 6-8 feet because Smith K-frame service stocks, when grabbed very rapidly, point way right in my hand. A Kahr 9mm, when grabbed as fast as I can from multiple locations and fired from chest height will let me make a first round hit on an 8" target every single time at 7 yards - this by looking at the target, not at the pistol.
2. It can't hang up on anything, ever. The more protrusions, shelves, hooks and hangups it has, the more chances Murphy will use one to ruin your day. I practiced pulling an SP101 out of my back jeans pocket really fast - the hem inside the top of the pocket hung up on that little bit of cylinder sticking out past the recoil shield. An exposed hammer spur - fuggedaboutit - that hammer will catch on shirt tails, belts, hems, anything and everything. I had a gunsmith bevel the back of the cylinder, the back of the cylinder release and remove the hammer spur and that made it a very slick little piece to draw from front, back or coat pocket. But it still weighed about 1 3/4 pounds loaded and would really drag down any coat pocket short of a heavy parka.
3. It has to go bang reliably. Revolvers do that. All four Kahrs I've owned have done that. Not to tout Kahrs exclusively, I'm sure there are other brands just as reliable but they're the only ones I am familiar with in this genre.
4. Once it passes 1, 2 and 3, caliber is secondary as long as it is at least 35 and will penetrate 6-8 inches through heavy clothes - a .38 Spl or most modern 9mm ammo seems capable of that. When I'm startled, scared, in the dark, off balance, maybe stunned by a sucker punch (if I'm still concious - the one time I got punched like that in New Orleans by an "urban yute" I was), if I can put a really really really fast first round hit center of mass just by point shooting, that's the one for me. If I then have the opportunity to take an aimed or semi-aimed second or third or fourth shot, that means I'm still alive so those are gravy.
But I want to be able to yank that handgun from its hiding place in a blind panic, have it come free without hindrance and make a first shot hit. If it does that then what type of firearm it is is unimportant to me.
