Hello. You did not present the battles to which this question refers, nor did you present any text where we could look for an answer. This makes it impossible for your question to be answered accurately. However, I will try to help you in the best possible way.
To assess which battle had the most balanced number of soldiers on both sides, you need to know the number of soldiers, in each army, that was participating in the conflict. The battle that has the most balanced number, in this case, is the one where the two armies have a very close number of soldiers, or the same number. For example, if in a battle between Army A and Army B, Army A has 1000 soldiers and Army B has 300 soldiers, that battle has an imbalance in relation to the number of soldiers. However, if Army A has 1000 soldiers and Army B has 920 soldiers, we can consider that this battle is in balance, since the number of soldiers in each army is similar and each army will be able to attack and defend at similar intensities.