how did I know this was going to turn into a pissing match over brands and ammo?
If your life is truly in danger, a round in the chamber of a Mossberg, a Remington, a Beretta, a Browning, a Winchester, a Charles Daly, or even a New England Arms, will serve the purpose. My personal preference is Beretta, or Browning, but that is because I come from a clay target sports background, and that is what I shoot and see consistently on the skeet fields and sporting clays courses. I know that both of these guns go BANG every time I pull the trigger. Neither of them have ever had a failure that wasn't directly caused by shooting poorly reloaded ammo. For home defense I use ONLY factory loaded ammo, and I have never had a failure to feed or extract in my semi-auto Beretta with factory ammo, nor have I ever had a failure to fire in in my Browning (it's a Citori, an over and under) while using factory loaded ammo.
Take a safety course, and a home defense course. Purchase the best quality weapon you can afford, practice regularly, and keep your weapon clean and well maintained. THAT is what important. Oh yeah...and if sounds like bullshit....it probably is, the best source of information on the local laws is going to be from your local law enforcement (before you have a situation), or a reputable home/self defense course being taught locally.