Accuracy means many things to many people. Can you consistently shoot 2" groups at 25 yards? If you're ever in a gunfight will your life depend upon whether your gun is that intrinsically accurate? (Nope!)
Reliability is the primary criterion for selecting a defensive handgun. No matter how accurately it shoots, if it doesn't shoot every time you pull the trigger then it's not reliable enough. I'll sacrifice accuracy that won't make a difference to reliability any day. Reliability breeds confidence, and you have to believe that your gun will work otherwise it will be one more thing niggling at your concentration when you need to be thinking about more important issues.
I'll make a bold statement: ANY defensive handgun model (and derivatives, i.e., the G27 versus the G22) on the market today that is sold to LE or military agencies, using US-manufactured new ammunition, is MORE than accurate and reliable enough so that your life will not hang in the balance... IF you can shoot (and most people can't).
I'll make another bold statement: the true test of a marksman is that he can hit with ANY weapon. I love 1911s and have several very expensive guns from the nation's best builders. I own Glocks also, and a S&W Sigma in .40, as well as several revolvers in various calibers and sizes from S&W. If I am ever involved in a gunfight, my living or dying will not depend upon the particular weapon I have with me at the time. I would be far more afraid of the likes of Clint Smith or Mas Ayoob with an Erma .22 single-action revolver than of your typical street punk with an Uzi.
To prove a point: I had a group of security officers from a large corporation who were qualifying at my indoor range complain about their issue handgun (S&W Sigma 40), and blame their low scores on the gun. I borrowed a new Level III security holster and belt, and the lowest-scoring officer's gun, dry-fired the gun a time or two on the range, and ran through the qualification with the next string... and scored a 248 out of 250 with a gun I had never fired before in my life. It's not the gun, and it's not the ammo... the shooter is the weapon and success or failure (living and dying) depend on both skill and attitude rather than your choice of handgun or defensive load.
I'm a big fan of guns that have the same trigger pull from shot to shot, and therefore I'm not a big fan of conventional DA/SA pistols. I can shoot very well with them, though, but it's one more thing to have to think about and I want a defensive gun that requires as little thought as possible.
So... pick out a gun that feels good to you, with the features you like, made by a quality manufacturer and with a good reputation, and you can't go wrong.
One final challenge: if you can't put five shots into one hole at 15 feet firing slowly and deliberately, then you need some serious work on your shooting. Remember Cooper: "Owning a gun doesn't make you armed, just as owning a piano doesn't make you a musician."