Vergil's hair when he was really like first delved into as "Dante's Twin Brother" they made him appear just like Dante and he slicked his hair back into a spikey kind of look that was when he was "identifying" himself as different than Dante. Still his new appearance doesn't really make him seem like Dante's identical twin brother.
well DmC Vergil's design was based off of a discarded DMC1 design. Though in the revealed DLC scenario, DmC Vergil's hair is looking closer to this than the neatly combed thing.