To correct the confusion...

Punches... Period.

Wordplay and Metaphors should compliment a punch.

A filler is just a line that is not a punch. Period.

Example:

A simple punch...

You're paranoid for thinkin everybody is laughing at you... though
We're not laughing at, But with you... Since your record's the joke

^ha ha ha... Very fuckin funny.

A Punch w/ Wordplay...

A flaming faggot, You'd give head checks until ya lips get hairy
To speak your language, I'd have to get the definitions from a Dicktionary (Dick-tionary=Dictionary <-- Wordplay)

^I'm dying with laughter

Punches w/ Metaphors...

I'd hate to son you, And I'm trying my hardest not to fuck you
Since you give better blow jobs, Than Christopher Reeves' lung tubes

^See the comparision? ha ha...

If there is no punch, Than voting on simply metaphors and
wordplay defeats the purpose of a Rap Battle. This isn't word
battle or whose smarter battle... But a Rap Battle.

No punch... Than there should be no win.

Oh, And flow is also as important as punches. Without flow, The
punches are nothing. Flow is Rap itself... And is a fundamental
not to be ignored.