I really don't know if there is a difference between the RR Racing and the Unorthodox Racing UDP, I don't think a side by side pic has been posted. I have the RR racing and like it, and there are people with the UR who like it too
I hear most of the gains come from it being a lighter weight pulley anyway, so go for whichever one is lighter maybe?
I think the RR Racing is cheaper, but I got it at a group buy price so I'm not sure.