Advance Wars is a turn-based game, so naturally, whoever goes first will have an unfair advantage. Look at this example:
It looks fair. It's symmetrical. What could possibly go wrong? Well, Orange goes first, so they can get to the cities faster than Blue can. Play it out in your head if you can't see it.
So what do we do to fix this? Well, we could do this:
Much better. Blue can get one of the cities first, Orange can get the other first. This map is balanced.
But giving the second player a free Infantry doesn't alwys work. Look at this:
Oh, look. Now it's as if Blue went first. We just gave Blue the advantage Orange had.
Here's another example:
This is just a bad map, period. And an exaggerated example. Orange has the advantage of going first, and if we gave Blue a free unit, then Blue would have the advantage. Avoid making maps like this.
Does either player have an unfair advantage on this map?
Actually, no. While far from perfect, this map would be fair to play on.
More to come at a future time.