First of all we all agree that Vergil probably awakened his Devil Trigger before Dante. The reason that led us to believe that is that when Dante awakened and attacked Vergil, Vergil responded "So..a devil has awakened inside you as well" or something similar to that. He looked pleased and as if he had a nice surprise. If he wasn't already able to Devil Trigger he would probably be surprised in a different way, maybe saying something like "What's gotten into you?".
Also, since I consider the Devil Trigger forms of Dante and Vergil in Devil May Cry 3 as incomplete/infant versions of their real forms, I think that Vergil probably awakened that power not too long before Dante did.
If we take the manga as canon, I would think that Vergil awakened when he had Yamato piercing his chest, even if that happened in some sort of illusion/other world.
Otherwise I think that probably Vergil awakened during that "year" where Dante & Vergil did not met. Remember that Dante said to Vergil "It's been a whole year since we last met". Probably Vergil was able to use Devil Trigger before meeting Arkham (as in contrast to the manga where Arkham meets Vergil when he is still a human, in their meeting in the game Arkham is already a Devil and leads Vergil immediately to the tower instead of where he was led in the manga).
My logic/intuition/feeling tells me that if Vergil was able to Devil Trigger for more than a year he would probably look more "complete" as a Devil.=]
Also, since I consider the Devil Trigger forms of Dante and Vergil in Devil May Cry 3 as incomplete/infant versions of their real forms, I think that Vergil probably awakened that power not too long before Dante did.
If we take the manga as canon, I would think that Vergil awakened when he had Yamato piercing his chest, even if that happened in some sort of illusion/other world.
Otherwise I think that probably Vergil awakened during that "year" where Dante & Vergil did not met. Remember that Dante said to Vergil "It's been a whole year since we last met". Probably Vergil was able to use Devil Trigger before meeting Arkham (as in contrast to the manga where Arkham meets Vergil when he is still a human, in their meeting in the game Arkham is already a Devil and leads Vergil immediately to the tower instead of where he was led in the manga).
My logic/intuition/feeling tells me that if Vergil was able to Devil Trigger for more than a year he would probably look more "complete" as a Devil.=]