The game is probably balanced but I think it is harder to play the axis. They need to balance defense and offense when the go into Russia with Germany, Japan needs to be careful if it does not hold Hawaii because then its captial could become in danger if its initial starting air force and navy is off conquering the world. Also Gilbartar can cause all sorts of problems for the axis if they are not careful, the allies can hit a lot from there. Italy can get jacked up by Britan if Germany does not at least threaten Sea lion and the Brits fly 4 planes to Africa from Pacific.
It is too early to know for sure if such a huge game is balanced but I still think it is at least close. Those are just the observations I have made about the Axis being harder to play.