There are SO MANY factors involved even within hours not to mention days that will change the results of a dyno.
I will agree that the Hiper has much straighter bent and I'm sure that helps out with the flow... However, I also believe that B&B has lifetime warranty which is very important to some. I also think that the B&B is much better quality product.
Anyway, bottom line is that there are too many factors involved in order to say "for sure" that the Hiper had better results then B&B based on how it was done, period. So, get what you want, get what you like, get what you can afford and you will still have a kickass exhaust! Why? Because its on a Z!!!!!! :)