Take it skill by skill.
Aerial ability: I think Sanji wins here, and this is 1/2 Marco's top skills. Sanji is already naturally fast, but with raid suit he's one of the fastest in the verse, probably only second to Kizaru or maybe his bros.
CoA: Let's give this to Marco. Sanji's CoA hasn't been impressive.
CoO: Sanji. He dodged attacks from a YC1 FS user.
Endurance: Marco. Obvy.
Durability: Sanji. Vinsmoke raid suits were tanking an entire Yonko's crew, including Commanders, shooting bullets at them.
Attack Power: Inconclusive. Marco's strength comes from his aerial ability. With RS, Sanji surpasses him there. He will pick up far more speed/momentum than Marco, but Marco's CoA should be better.
Agility: Sanji, and not only is he more agile, but he is also INVISIBLE.
All in all, I'd say Marco's endurance would make the difference here, but this would be a very high diff fight.