Bipolarity and multipolarity aren't really theories about "war" so much as systemic theories about international relations in general.
This question is oddly phrased, but I'm assuming that the question is asking which system more closely explains/resembles the current situation in the world.
Well, the best answer for that would be unipolar. The United States is currently the world's greatest superpower. America is a global hegemon and no country can really compete with US ...
The solutions explains the theories of bipolarity and multipolarity as it relates to current international relations and conflicts (war).