Neither traits preclude someone from being chaotic. Marv took things as they came, and was about as disciplined and formulaic as a kitten on meth.
The man was chaotic, and while compared to the other, actually evil bad guys in the film he wasn't on their level of wicked, he wasn't exactly good, either.
Marv was an anti-hero. That was the point of the character. He was the marginally bad guy that you root for, fighting the throughly bad guys you don't.