You know what I find a fun background tidbit?
Or the fact that he only spikes it up because of Dante. At least in the manga.
Like, we know he used to keep his hair spiky before the fire. Either this was something Eva did for him or he did it himself to differentiate from Dante.
But then the attack happens and he loses his spikes for the hair-down style his brother is known for. And Vergil does not put it back up again as far as we can see.
Not until the dmc3 manga that is.
There we still see him walking around with his hair down, even meeting Arkham like this.
You wanna know when he starts spiking it up again?
Well, it's right at the moment Enzo confirms to Vergil that Dante is alive and in the city!
Look at him being all dramatic!
So yeah, if you ignore what the games provide in this regard, Vergil probably kept his hair down during the entire decade he and Dante thought each other dead. Maybe it was Vergil's tribute to his younger twin or it was just him not seeing a point in styling his hair like he used to, because who he was supposed to set himself apart from was already dead.
And because of that, as soon as Dante is confirmed to be around still, he's got reason to do so again. Least of all to not be mistaken for his brother by more drunken people xD