6'7' makes me forgive Lil Wayne for all of his watered-down guest verses and lame puns. He slays this beat by Bangladesh (that fits squarely into the A Milli template). Let's break it down.

Lil Wayne's delivery is in a slightly higher register here than it normally is. He isn't straining, but he is delivering his lines with force and in quick succession. There is a tight bounce on the beat and he isn't going to waste it for some loose rapping. His rapid fire delivery adds momentum to the beat and, at times, provides an additional percussive track.

Lil Wayne's rhymes don't make a ton of sense and thus they all make complete sense. Most of his lines would seem out of place if delivered by another rapper, but because he has been dwelling in the abstract for so long, this is sort of expected. For instance "Niggas think they He-Men, pow, pow, the end." What? Let's put in context with the line immediately preceding and following it

Swear, man, I be seein’ through these niggas like sequins
Niggas think they He-Men, pow, pow, the end
Talkin’ to myself because I am my own consultant

It just comes out of nowhere. It is ridiculous and childish and esoteric and somehow totally acceptable. To further emphasize the point, when Cory Gunz handles the final verse, both his delivery and his rhymes come off as flat, non-sequiturs delivered by someone who sounds like they are a bit too conscious of what they are saying. For instance

Word to my mama, I’m out of my lima bean
Don’t wanna see what that drama mean, get some Dramamine

Out of your lima bean? What? Do you really mean that?

To the contrary, I am quite certain Lil Wayne is insane.

In short 6'7' > A Milli.