It depends on what kind of look you like and what you are going for.
(I don't remember what managraphic I liked to use on my Rizelea because it has been a while since I've played.) Out of the two choices there, I think the Phalia Star matches better. However, if you prefer an "edgy" weapon that would really stick out, you could use the Castase to achieve that. My personal preference would probably be the Phalia Star. Best of luck with the decision.