Well I would go for zorua because once it reaches level 60 and is very friendly to you it is strong. I used it against Zekrom in B2 and the first time I used foul play and the second one was always a critical hit for me. I had to keep on redoing it until it wasn't a critical hit. This same thing happened with kyuerm.
I would get zorua. After you eveolve it and it reaches lvl 60 and is friendly to you it is very strong. Even against types that would not be so affective