If Kidd is that stronger than DR / post TS Luffy, this makes me think
In 1 vs 1, DR Law is actually stronger than DR Luffy too
DR Luffy's only big gun is G4, while the others straightly got laughed by Doffy. But that version of G4 only lasted a bit and after that Luffy became sitting duck
With Law's endurance, intelligence, and versatility it's very possible to think DR Law can outlast 1 round of G4, mainly by teleporting around and confusing the dumb gorilla. After that, it's game over for Luffy as he is a sitting duck
Now comparing Luffy's ultimate move vs Law's ultimate move
KKG vs Gamma Knife
Well, Law can't survive KKG but Luffy also can't survive GK. But it's easier to land GK on the gorilla than to land KKG on intelligent Law (especially if Law uses it to sitting duck, post G4 Luffy).
DR Law >~ DR Luffy