I have seen it very very even. I played two games and I am 2-0, one with allies and one with Japan. Both against very good but not spectacular opponents (Im not great but I can be creative and level headed). The games were slugmatches from the very beginning.
Both games were won and lost in China and the victor was able to play a better game of cat and mouse with their American/Japanese navy. Its probably the best and most balanced axis and allies expierence I have had.