Cheren, all the way. He's arrogant, and his pokemon can (kind of) back that up, whereas Bianca just kinda runs around annoying everybody. And also gets a pokemon stolen, and just whines to Cheren and us about it. Cheren is a "get up and do it yourself" person, Bianca is a "give me what I want without me working TOO hard for it" person, IMO.