Let's not forget that the Axis nations would have had a large population of surly underlings. With Communism as the only viable alternative, they all become Commies. The Axis nations can't fight the whole damn world.
The thing is, the Communists also had a huge population of downtrodden underlings, many of whom thought that going Nazi would be a splendid way to escape from the Russian rule of terror. It's not that one system or the other would have been better or worse for the in-between people, in absolute terms - it's just that any competing system was automatically better than the current one in offering at least some hope of an eventually brighter future.
Polarization of the world because one player gains in power is by no means a given. Earth has experienced several periods of history where one or two absolutely dominant powers emerged on a continent-wide scale or better (e.g. China has been doing that for some two millennia in a row now), and smaller players nevertheless continued their game as usual in the immediate geographical, economical or political vicinity. A Nazi victory might have jolted the world, but as for making it more uniform...
you're overlooking something-Communism has potentially universal appeal. Anyone can be a Communist.
Nazism is inherently limited because of its racialist/Ubermensch nonsense. It could NEVER have appeal to Blacks, Jews, Gypsies, the disabled, gays, feminist women, etc.
in a global contest between the two, the Commies have a wider base of support.