They are similar, but different. For example: creatures from the seventh game have higher minimum and maximum damage, but lower attack stats, and the cost of hiring creatures in the 7th part is significantly higher than in the 5th, and so on. In general, in order to have some kind of balance, the other factions need to be adjusted as well.
Added 5 minutes later
For example, in Heroes 5, the damage is calculated using the following formulas:
- If the "Attack" of the attacking squad is greater than the "Defense" of the defending squad, then:
Total damage = number of attacking creatures * damage * [1 + 0.05 * (attack - defense)]
- If the "Attack" of the attacking squad is less than the "Defense" of the defending squad, then:
Total damage = number of attacking creatures * damage / [1 + 0.05 * (defense - attack)]
Added 2 minutes later
In Heroes 6, units don't have attack; they only have damage, and defense reduces damage in percentages (i.e., if physical defense = 9, then physical damage is reduced by 9%). I don't know about games 1-3, 4, and 7.