I think I mentioned a short reply on another site for ya.
Basically, the P99 A/S is my fav gun of all time.. I'm not that big of a fan of the QA trigger - as it is heavier. But, it is a very short pull. SOme people like it.
Frame wise - it is the same gun. Pretty much, the only difference is the trigger action, and a smaller decocker button. The A/S is kinda hard to track down. Typically, ya gotta have your dealer order you one. They are not importing them in very large numbers.