As a fan, I want to say Philsulin.
Judging from the IFBB judging standard, Kai wins.
I think thats pretty accurate of things, who wins is gonna be determined by which way the judges are going to go... Going by their track record, Kai is going to win, they always seem to go with the complete conditioned mass monster over the guy with the full muscle bellies and small joints, See Dorian vs. Wheeler, Ray, Levrone, etc, Coleman vs. Wheeler, Levrone, Ray, etc, Arnold vs Sergio, etc.
People like to say that the IFBB judging is all over the place, but if you really look at the O, theyre pretty consistent with which physique type they reward.