Obviously, everyone has different views/preferences when it comes to safeties on guns.
My own personal preference is for no manual/grip safeties, but with a long and/or heavier trigger pull, for a self-defense gun. There's less of a chance for something to go wrong if I'm forced to use the gun in self defense. I've owned 1911s and have never failed to take the standard Colt thumb and grip safeties off during the draw, but I've never had to do that while someone was trying to kill me. I also like the safety hedge that a longer and/or heavier trigger pull offers.
I also like guns with external hammers, again for that little extra margin for error in terms of holstering safety. Like many people, I was taught to ride the hammer with my thumb when holstering. I don't consider it essential, though, particularly if I have the longer/heavier trigger pull. I carry a 642, though I admit I would love to get a Bodyguard J-frame not because it has the option for SA but because I can ride the hammer with my thumb while holstering. That's something I can't do on the 642.
The most important thing, though, is safe gun handling regardless of whether or not your gun has a manual safety. I like having those extra little safety features (long/heavy trigger, external hammer, etc.), but I wouldn't rule out using a Glock, Kahr, or similar type of gun simply because it doesn't have those features.