The Oerlikon has the highest practical ROF, the Flakvierling has a slightly longer range and the Type 96 is not really a point defense system, more of a medium range weapon like the 40mm Bofors. The Japanese point-defense gun was the twin or quadruple mounted 13.2mm Hotchkiss. The Free French had them too, and ditched them for Oerlikons when they got the chance.
In terms of putting as much lead in the air as possible the Oerlikon is probably your best bet. They don't require much deck space or infrastructure and spit a lot of shells.