It's actually kind of hard. Bravo can easily pick off alpha soldiers when they reach the bridge. The lower route is basically useless for Alpha since it passes both the bravo spawns, so all Bravo has to do is keep a good watch of the opening before the bridges. The jet level makes it kind of hard for alpha to make a speedy escape... In my opinion it's fairly balanced.
If more people disagree, i can move the flag to the lower route or something.