ORIGINAL: Tanaka
I wonder what the big difference is?
There are several, but the most important one - in my honest opinion - is a 2nd front in USSR. In WiE you won't be attacked by Japan. In WaW - probably as soon as JP DOWs USA. Against all-in attack Russians need plenty of units, and they already lack them against Germany.
2nd difference - map scale. In WiE, although there are more turns across the year, you have to get through a lot of hexes. In WaW not that much, and with 6AP Panzers you will get to Perm from Moscow in ca.3-4 turns.
SC:WaW IS generally well balanced. But if you take a very good Axis player, then he will win majority of games against similarly skilled Allied player. Simply by leveraging early game advantages. There are plenty of AAR's in these forums between good players, Axis wins in almost all of them. Fortunately (?), there are not that many that good Axis players, this requires a lot of skill.