I have both, a pair of Rosys (White Waters) & 2.10 Balls (assorted morphs). My opinion is you can't go wrong either way. I've found the Rosys generally a little easier to handle. Balls also have that unpredictable lack of feeding habit were a Rosys feeding habits are a little more seasonal.
Either one you choose, besure to one that's at least acouple of generations captive bred. Personally I've found multi-generation captive bred animals do better in the long run.