In reality, a commander very seldom attacks without an advantage sufficient to believe he might win. When attacking a prepared position, a 3-1 advantage is usually required by the attacker. Of course there is always the odd chance that 300 Spartans will stop 100,000 Persians, or 200 Texicans hill hold out for days in an old mission.
Meeting engagements are relatively rare. it is much more common for two forces to meet in battle with different objectives, hence the reason why may there are historical battles where both sides correctly claim victory.
I'm very much a fan of "unbalanced" scenarios. Would Leonides be a hero in a 1-1 meeting engagement?