He will probably win, not because he is stronger but because storywise that makes way more sense.
Hancock beats mercilessly Coby: he is taken captive/turned to stone/killed. Nobody cares bar maybe Garp and Helmeppo who are pissed/want to take revenge/free him (weird route).
Coby beats Boa and capture her: we have multiple possible routes, Coby actually beat her and we will find her again if and when Luffy will try to free Sabo (some kind of Impel down 2.0) Coby and Boa recognized eachother as Luffy's cheerleaders so they devised a plan to free Sabo etc. At the same time Coby starts to get credit as some kind of Luffy marine rival (or at least future rival).