This is either a very elaborate troll, or I came to hate you in the last minute.
Dude, I was joking. I loved Vezlid's post. I totally agree with him. Old Vergil is a living anime trope.
New Vergil is optimistic, and yet is still pragmatic. He cares about people, and still knows the need for sacrifice. This is a character with a lot of layers. And, as you'll see later on, a very dangerous person who will not let anyone, including Dante, from completing his mission.
He only agreed to rescuing Kat only because he thinks there's still a small chance to reach his goal while still being able to abide by his brother's wishes. However, later, a situation will probably arise where he'll have to make a choice: the mission, or Kat. Dante will choose Kat, Vergil will choose the mission, and they'll fight because of that.
This is what most likely will happen. The same goal, but two very different ways to go about it.
But it makes sense; rescue one person, or free humanity from the demon's grasp? It's a tough choice, no matter how you look at it.