In RS I mainly play on Axis, like I mainly play on Allies in RO2 (I prefer their weapons), and I have a roughly 50/50 win ratio. I find the Allies ridiculously easy to play on and rack up kills, but it can be difficult to push if the Japanese have entrenched themselves well enough. On the Axis side, however, I play more carefully, have to try to take out everyone before I can jump into the cap zone (DAMN THOSE BAR CAMPERS), and am on constant lookout for Flamers, but it feels more rewarding when I am successful.
So long as you know the map, both teams can win, but if both teams are equally skilled, more team work and coordination is required for the Japanese side to win.