>>43068810some were just reskins, others like captain black dino had a boost to his intelligence. yes, "Captain" monsters were essentially the same, but with a boost to a specific stat. Monsters from this game did not differentiate too much, but many "reskins" has a certain ability or stat boost which made them superior to standard monsters of the same group.
very similar to pokemon. it is why your dark type mightyena will never be as good as your dark/fire houndoom