Sorry, but isn't this exactly what User said?
The problem with useless people saying useless things is that those useless things tend to spread.
When gyrocopters (player 1) are deployed against balloons and gyrocopters (player 2), the exchange is always favorable to the gyrocopters (player 1), except in the specific case where balloons actually manage to hit enemy mortars or catapults.
For that to happen, gyrocopters must not shoot down all balloons before they fire. If this becomes structurally impossible, then fielding balloons becomes pointless.
And upgrades clearly favor gyrocopters' attack over balloons' defense.