Stoptech's work extremely well on the racetrack, period.
I'm inclined to think that your 50 foot drop in braking distance is more a factor of driver improvement or driver confidence rather than the actual effectiveness of the brakes. As long as the brakes are within the temp range of the pad, they will both stop the car very similarly.
I raced for a full year on the stock rotors and calipers. We had them set up where they would not fade. Switching to Stoptech's made my life easier because they are more consistent, have a better feel and run at lower temps, thus not ruining everything around the braking system. But they did not drastically decrease my stopping distance. Probably a few feet.
I could see you losing 50 feet of stopping distance if you were experiencing pad fade with the stock system, but you can't compare the two. If you used a hot pad and a hot fluid in the stock system, they wouldn't fade and then you could make that comparison.
That said, after using the Stoptech system for 2 years, I can say the Stoptech's are an awesome system that can easily handle full on racing for extended periods of time.
Sheehan Motor Racing