Blackbeard seemed confident in facing Sengoku with his crew, yet retreated from Akainu. Even though the situations were different. with Teach having little to gain from fighting Akainu, it seems to be a strong indication that Akainu > Sengoku.
As for everyone's reaction to Garp punching Marco, it might've been due to them being surprised he'd make such a solid stand on letting Ace be executed.