I would put it on the wizard. It makes sense to try the cc guy's initiative up, but he will have 5 from the other pc's 1 trait leadership anyway(so you only lose 5, not 10). The other leadership bonuses aren't really good for caster wizard(cc%, damage%, armor%) and knight/fighter will probably need talents more(man-at-arms, weapon, defenses 2-5, maybe aero/rogue/crafting dabbling).
