The outcome of the fight should not be controversial, Zoro always was and always will be the guy right after Luffy and Sanji is always going to be the guy after Zoro. I guess the controversial thing is the distance between them? Honestly I think, Thriller Bark answered everything about Zoro vs Sanji. When Luffy was down the one to fight Kuma was Zoro for the most part Sanji only came in when Zoro was in trouble, the rest of the crew didnt do anything. Ultimately they werent able to beat Kuma but 2 things were finally confirmed Zoro and Sanji are much stronger than the rest of the crew and Zoro is above Sanji. Oda putting only Sanji in those scenes with Kuma. Tells us Out of all of luffys crewmates Sanji is the only one that Zoro cant Low Diff or defeat easily. That leaves us with Mid diff and High diff. With all the arguments/ and rivalry behavior of the two that Oda constantly does High diff sounds reasonable, But Mid diff also makes sense too in terms of the Characters roles/ motivation.