Straw Hats, high diff.

I think it's a narrow win for Straw Hats, since Shamrock is basically the big bad boss that Luffy will inevitably have to get stronger in order to defeat

Shamrock is not stronger than Luffy.

[Spoiler Alert]

We've seen in the last chapter that he's not even staying on Elbaph anymore. I still think they will call him back if the God's Knights have to fight the Straw Hats, but that's just a theory.

Shamrock is not winning aigainst a whole Yonko crew .