I believe Luffy would win in a battle between the two of them. Luffy has not really gone all out, plus the battle with Hody Jones was very limiting on Luffy's power. Since he had to fight in the sea in a bubble with limited movement while Hody kept "powering up" underwater, it was not in Luffy's favor to win against someone who could mmore freely and not be affected by the water. Plus, Zoro probably could've beat Hody as well but, in the water, he would not have been affected as much as the water's effect on Luffy. In the battle in Dressrosa at the moment, Zoro does not seem to be able to beat Fujitora or even Sabo if he tried. Same goes with Luffy. Also, Luffy has been fighting against Vice-Admiral level opponents in the Colosseum and went fully into a war with Doflamingo while Zoro was hit by Fujitora, an admiral, once. Also, it may seem like Luffy's going all out but you have to remember, he's a rubber man. All the attacks he does, he has to pull and bring back his fist many times over and over, in both gears as well. Zoro has swords in which he can do power moves which has a haki-imbued state if he wished. In a match between the two, it can go either way, but Luffy is always at a disadvantage (except for the Skypeia fight) and if Zoro wins, it might be a small margin, but if Luffy wins, it would be a win against someone would has a one up against Luffy's disabilities. Luffy's fighting power is balanced against those without a devil's fruit or without a devil's fruit that isn't supposedly "useless" like Luffy's.