Greninja is the best design of the 3. Also water and dark is an interesting type combo. On the other hand, Chesnaught is atrocious looking. But, Grass and fighting is a pretty cool type combo, except for the 4x weakness to flying and also Chesnaught looks like a rock guy rather than a fighter. Delphox got an awesome type combo. Fire and psychic, and his design is kind of decent.

I'm going to go with Froakie for my Kalos starter and Charmander for my kanto one. I'll be getting x because of the blue charizard and the badass fighting mewtwo.