How is he gonna get stronger in a jail cell 23/7 with handcuffs robbing him of his powers the entire time.People forget that Crocodile's best feats where during MF.
He is capable of clashing with Mihawk receiving zero damage. He repelled Akainu and tanked Jozu's brilliant punk surprise attack with little damage. Its safe to say he did not use anywhere near full power against Luffy at Alabasta, or he simply got a lot stronger in jail. I would put MF Crocodile just under Luffy, with Haki, he is probably equal with him.
Regardless I think Megallan wins the first scenario because he is the perfect counter to Crocodile. The second scenario is a toss-up, leaning towards Croc.
Crocodile clashed with one blow from Mihawk, that's it. That's only because his hook is made of a gold alloy, so it's extremely strong. You should also take into account Mihawk was aiming for Luffy, so it's not like he was putting 100% of his effort into that swing.
He didn't tank Jozu's hit, Jozu knocked him off of his feet and sent him flying. Granted, it didn't leave significant or lasting injuries, but he didn't tank it either. If Jozu had continued slamming him, Crocodile would have died.
He didn't repel Akainu either, he launched a sneak attack from the ground that cleaved him in half because Akainu's body reflexively turned into magma, a semi-liquid. If Akainu and Crocodile went one on one, face to face, Akainu would plow through him.