I actually sometimes like the teams being unbalanced that way.
I'm new to flight sims (very new) yet I've been very active in RTS, FPS etc...even in RL events ie. paintball etc...it is fun to sometimes have unbalanced sides.
Sometimes the challenge of surviving against insurmountable odds is very exhillerating. I've seen odds turn based on strategy alone from countries with lower numbers.
I've chosen to play Rooks in AH, mainly because after playing all 3 countries I found the camraderie with the Rooks more to my liking, however I've found that with rooks sometimes we are heavily outnumbered at times, and before I can get fed up with it the tides turn and now I'm on a team with superior numbers.
Like I said, I'm a newbie, so some of you are apt to take what I say and ignore it, however; I've learned long ago not to just join the superpowers and gravy-train it through a game. I have an absurd kill ratio, and it is steadily improving, yet the thrill of insurmountable odds at times keep me addicted.
If you're one to want game balance, play on the team that has the medium of players. That way you have one enemie with superior power, and one with inferior. If you prefer dominance, join the country with the most pilots. Or, if you're like me, choose the cheesy team and pray for the best.