There's just ACCURACY.
Owning a large indoor range and retail gun shop for a decade, I got the chance to shoot nearly every modern handguns (and lots of no-longer-made ones, too!). I have yet to see a brand-new modern handgun that was not defective (in other words, what we'd expect when we'd buy one) have unacceptable accuracy for defensive use out to 50 yards... meaning they'd all shoot within 8" at that distance and do considerably better at closer range. I've never shot a 'first-tier' handgun from one of the industry leaders (Colt, S&W, HK, Glock, Taurus, Beretta, Sig, etc.) that couldn't put 5 shots into a nickel at 7 yards, slow fire. That's intrinsic accuracy. BTW, those first-tier handguns will usually shoot palm-of-hand-sized groups at 25 yards, offhand, slow fire... certainly good enough for that all-important first shot at extended range. But if you're planning on hitting a bad guy with a hostage in the eyeball at 25 yards in real life with your defensive handgun, you need to stop dreaming and come up with a better plan.
Now, intrinsic accuracy and usable accuracy are two different things. Some guns are more ergonomic than others, and some guns are better-suited for defensive use than others. For instance, it will be hard for any shooter to obtain the intrinsic accuracy of, say, a super-light titanium .44 Magnum with full power loads, in a defensive situation. The gun will kick too much, it will hurt too much, and you will flinch too much. That's why such guns-and-ammo combos don't make good self-defense weapons against man or beast. As Dirty Harry said, "A man's gotta know his limitations."
Re some people's reported 'accuracy' tests (shooting as fast as they can and blaming the gun if they miss), that is really a shooting SKILLS test. Don't blame the tool if the user isn't capable. Nevertheless, such a test does point out some valuable information.
First, choose a gun for self-defense that has a minimum level of acceptable power and that you can hit with, under stress, repeatedly. For some, that may be a 10-shot S&W 617 revolver (which, with CCI Stingers, isn't a bad home self-defense gun). For others, that may be a Glock 17. For others, that may be a 5" 1911 shooting 230gr hollow points. And for others, that may be a S&W Airlight shooting .38 Specials. The point is, only hits count. And, it's better to hit with a .22 than miss with a .45... just as it's better to dump a magazine of 9mm into a bad guy than to get one shot off with a .44 Magnum.
Second, if you can't hit when you're firing deliberately in non-stressful conditions, do you think you have a chance of hitting when it's dark, you're scared, and someone's trying to kill you?
Here's a good routine to use when going to the range with one 50-round box of ammo. Fire in 5-shot strings (that gives you ten 'relays'). The first two relays (10 shots) should be spent doing slow fire at 10 to 15 feet, aiming for the center of the bullseye on a standard pistol target. If you can't shoot a one-hole group at this distance, then either your gun is woefully deficient (doubtful) or you are flinching (probable). Line the sights up, press the trigger slowly, and be surprised when the gun goes off. What these two relays do is verify that your shooting technique is solid. Then, start shooting faster. The next two relays, bring the gun up from the low ready position and try to fire five AIMED shots as fast as you can, at 10 to 15 feet, at the center of the bullseye. Your goal should be to get to where you can fire each shot less than 1 second after the previous shot and get one ragged hole. This is important: only shoot fast enough to get center hits, and no faster! After two or three relays (and half the box gone) you should start feeling a rhythm developing and your speed should start increasing. Keep this up, pushing the speed slightly for each additional relay, but NO faster than you can get CENTER hits. For the last relay, bring the gun up from the low ready position and fire five shots just trying to keep them in the center of the paper with a flash sight picture (the bulk silhouette of the gun aligned with the center of the target -- how you'll probably shoot at 10' in a real defensive situation anyway -- but try to at least pick up the front sight).
You'd be surprised at how doing this for a few weeks will help your shooting.