Since you restricted susanoo, cursed seal and possibly enton as well, I guess Oro wins low difficulty. Also does Sasuke have enton or is that restricted to? The Sasuke that fought Killer Bee was at his weakest since the beginning of Shippuden. Early Shippuden Sasuke was stronger since he had the cursed seal but the one who fought Bee did not and he admitted himself that he can't beat an Orochimaru who is at his strongest.
Amaterasu is countered by shedding his skin and early Taka Sasuke can't spam amaterasu without drawbacks. Lightning, fire and kenjutsu is pretty useless against Orochimaru. the only thing going for Sasuke is genjutsu but Sasuke's is weaker than Itachi's and I'm sure that a genjutsu won't permanently stop Oro. Oro should be smart enough not to look Sasuke in his eyes after all the mistakes he has made against both Uchiha bros.