Which cube is the best for raising a potential to legendary?

From my experience with the new cubes (2.9k ea) was horrible, I did 6-8 sets and only went from epic to unique DURING Double Miracle Time. After double miracle time was over, I used the rest on my weapon ( was already legendary) and was just trying to cube for stats. That also turn out bad, I didn't get any good pdr or boss %, BUT I did get 30% int, 27% luk on my katara -.-

With Super I got the stats I wanted for my katara with just 2 sets. 35 boss 30 boss 30 pdr =). Overall I"m not satisfied with any cubed. The only cube I like is the Enlightening one.