How is Law stronger than Zoro exactly?
I took it from Law's performance until Dressrosa. To beat Smoker, and after that beating Vergo altogether with slicing open a literal mountain at once, and after that fighting Doflamingo, and beat Trebol, is a consecutive feat that is more than beating the Pica, the mountain version and the original version imo.
Against Hawkins, Zoro was pressed by Hawkins' doll, while Law subjugated Hawkins.
Against Kaidou, Law had Kaidou calling him little monsters, and also Law's attack trigger Kaidou's scream. Zoro's feat didn't reach that.
Those were the reasons for me to pick Law over Zoro at least until now. But if Zoro keeps showing new powers, i think he'll come out as superior.