I have the Stoptech kit and they weighed the brakes on a scale much more accurate and expensive than the one I have. The figures
were given in hundredths and even thousandths of a pound.
But I'll stick to OC's numbers since whatever error his scale might have had is at least applies to both the stock and the Brembo systems, so the weight difference should be relatively accurate.
I don't have the numbers for the Brembo kit but I would be willing to be that they do.