Law, easy win.
Zoro has shown that he couldn't keep up with Law's speed (teleporting) both physically and using CoO. Law in my opinion would easily do exactly what he do to Vergo on Zoro.
Having caught up on this whole thread, I'll like to throw my own pence into the mix:
It was a metaphor
Not all ships have seastone. The marines travel the Grandline SOLELY using the Grandline. They travel to the second half by passing through Marejois (over the red line). They only sail through the calm belt when going to the 4 seas. Why would they go into the calm belt where there is no wind to travel around.. They want to get to places as fast as possible, if it's in the Grandline, they are sailing there in the Grandline. Also, it IS a rare material and we have seen many battleships... It would be highly illogical for them all to have their hull covered in seastone.
It was my understanding that Law's fruit was able to do whatever the **** he wants in his room. Also, seastone only effects DF users when in contact with them. Otherwise it's just like the sea, Aokiji could still freeze them using his powers and they would freeze. But they have been stated to be as hard as diamond and no one has been shown to be able to cut that. Smokers ship could have had seastone, not saying that it didn't or it's not possible that it did. But Law's fruit allows him to slice it in half. Don't forget, it's not breaking the ship, more splitting it like how Buggy splits himself.
Vergo in my opinion was quite clearly portrayed and displayed as the strongest executive. One of Doffy's most trusted crew members AND the most proficient in CoA. He may not have had CoO mastery, obviously didn't have future sight. But to say he wasn't at least proficient in it? He blocked and dodged Smokers attacks. As for CoA, he tanked Sanji's attacks as if they were nothing. Sanji who has been highlighted to be more CoO focused could realise right after that first (maybe it was second) interaction and commented that Vergo was like a mass amount of iron or something.
Lastly. Garp. He's the perfect example where rank means nothing. He wanted to keep his status as a VA purely because he didn't want the responsibility that comes with a higher rank, but we all know he's much more hella strong than any VA or even admiral! Not to mention Smoker himself, we get introduced to him when he's a captain? He was much stronger than any other captain and then some! Rank means nothing in a battle, it could ultimately come down to simple match up.