Just to make it perfectly clear: vJass doesn't actually add anything new, everything that can be done in vJass can be done with regular JASS.
This is because Warcraft would otherwise not be able to read it (there are certain projects that do add new stuff, such as RtC, but those require a modified version of Warcraft to play).
vJass just makes those things nice to read and write. It's there to make your life easier.
Because of the way it handles code, it's been a massive help to everyone willing to use JASS. You can easily add and use libraries, change spells/systems and much more.