Mihawk>Shanks, and its not even close.
Do you think that Mihawk can lose an arm vs sea kings? No fking way, he can be relaxed to the max that thing wont do shit.
Shanks is just that weak, we can make a fair point that Usopp>Shanks because relaxed Usopp can take hits from tobi roppos, a sea king wont do shit to him.
Oda was smoking to much when he made Shanks lose vs some random fish.