I would have to say that if Mayuri's poision works then he has a good shot otherwise Orochimaru would probably dominate the battle, Mayuri doesn't come off as particularly fast so he would actually have to battle against him and I honestly don't see him overwhelming Orochimaru.
Poisons vary greatly from kind to kind, certain variants attack the nervous system in numerous ways, others deform enzymes and proteins.
That said, I see no reason for why Orochimaru would be able to resist Mayuri's poison. Also, Mayuri displayed rather amazing speed when he fought and kept up with Uryū.
Not really different from a body flicker- Orochimaru and the other sannin were able to leap around the boss summons like little blurs.
Oro did give Sasuke high general poison resistance, it's unlikely he'd not do so to himself.
One additional poison resistance tactic he has- body mass. Turn into a massive 8-headed snake. Any poison'll be incredibly diluted, aside from any other biological resistances.