In an arena focusing on a certain area, I'd say the best battles would be:
Wordplay:
@
Dissizit vs. @
Rican
Vocabulary:
@
Black Book vs. @
RhetoriK
Metaphors:
@
DaDDiO vs. @
MAN DOWN
Punchlines:
@
RULE vs. @
UNKNOWN ARTIST
Multies
@
GRizzEAT vs. @
Askari
This is a quick jot-down, all applying to the artists at their primes. It's not exclusive either, I'd put Askari down for vocabulary also and punchlines. Daddio for multies. It'd be an interesting tournament/league to create and have each league based on each style and have appointed voters for each league. In an ideal world, with a lot of effort, it'd be possible. That was what I imagined anyhow, put down your opinions.