It depends, really. If you're looking for a straight answer, you can stab me now. ><
Anyway, casually I'd go for Eevee because of the many different evolution forms it can choose to morph into, but the drawback of many Eeveelutions besides Espeon is that the're almost always only good for Baton Pass, with the exception of Espeon as a Magic Bounce/Dual Screen lead, Sylveon as an Assault Vest attacker, and maybe even Vaporeon. Not to mention that Eevee flat out wins novelty and design wise.
However. Minccino is an absolute beast in the LC metagame (where Pokemon are played at Level 5), and it has wonderful abilities in the form of Skill Link and the much coveted Technician. It also has wonderful attack stats in the LC metagame, and can learn a variety of moves such as U-Turn, Aqua Jet and the like to back it up.