Dick. He is one of the most fleshed out characters in comics, and one of the most admirable. He is essentially the arche-type for characters that develope as they age, as he's been in the superhero biz since he was like 8. As stated recently in Infinite Crisis, it is because of this that he knows everyone, and superheroes are his family. And he's not a douche, like Batman!
Tim comes in 2nd for being the best Batman protoge`. Nightwing isn't really Batman. While he's good at detecting, he is mainly a fighter/leader. Robin will be really great as the solitary figure solving crimes.