Geek,
I have used both white and black pepper in that rub. I find that they smell and taste enough alike that I will forgo the more expensive white pepper unless it is a soup or sauce where the black flakes would look funny. As I said, I copied that directly from the one that cajunsmoker posted, the question might better be directed his way.
How about that for a good non-answer??
Take care, have fun, and do good!
Regards,
Meowey