When i buy performance parts like that, I base my decision on what I have personally observed in motorsports. I am a motorsports phreak. (xcept nascar) Mainly F1, ALMS, Grand AM, HSR etc. I have seen AP brakes on a lot of race cars, and i tend to trust that those parts are going to be good enough for my car. I don't recall seeing StopTech on any race car I have seen. That really doesn't mean sh*t, but this is my dimented way of doing things. For all I know there are a billion race cars around that have them, but i dunno. I am heading to the 24 hours of Daytona (staying up all 24 too) and I'll be roaming the paddocks, so I know I'll be looking at brakes. Anyway, if it were me, I'd opt for the AP.