snovi,
If you are new to handguns, I'd say get the QA. It is a bit more simple to operate, and one need only about pulling the trigger when needed (not transitioning between the first DA shot and second and subsequent SA shots of the AS system). When I first started learning, it took me a while to not accidentally discharge that second shot (single action) after the heavier first DA shot. It can be learned, but for practical purposes QA is probably the better weapon in high stress home protection scenarios (there's just less to think about).
More experienced shooters usually like the idea of having a traditional double action (DA/SA). It tends to offer more ways to fire the weapon. On the P99, you can retract the slide a bit and cock the striker to go right into trigger forward AS single action. With other pistols, like a PPK or SIG etc, one can pull the hammer back manually to go into single action. You can't do that on the QA.
Those that carry, like "tabor," don't dislike the partially cocked systems like the QA, but they'd prefer to have a striker at rest just in case. The heavier first DA pull is also a "safety" feature that many are comfortable with. Others that carry, and don't shoot a lot (like tabor said) might prefer the QA again because of simplicity.
Seems to me like you're leaning toward the QA. I'd go for it. Reading your other posts, it seems the notion of the QA system appeals to you more than the AS. If you already feel that you'd be more comfortable with the QA, then I think that makes your decision right there. Also, you'd be hard pressed to actually find a new AS these days. Good luck on your decision, happy and safe shooting.
-stunks
EDIT: spelling
EDIT2:
Also, concerning the widespread proliferation of DAO-like (glock's safe action, XD's USA, Walther QA, and others) trigger configurations, it is a trend that is fueled mainly by Glock's success in the law enforcement market. Other manufacturers want a piece of the pie, too, so they come out with their own variations of the system. I really think that's why most new handguns have this kind of firing mechanism. Not because it is better than another, because it is what is making money right now. Again, there is no perfect gun for every situation, you'll need to decide what the perfect gun is for your situation.