I have no idea why the silencer worked so well, but it had zero recoil with a silencer and damage/range didn't seem to suffer, it was extremely accurate with no sway or recoil while firing and the hip fire was extremely good. The vector was extremely underrated in the latter months of the game, it was a very good weapon for online, and for some reason it performed best with a silencer.
I remember dropping some insane numbers with a vector in some small tournament I was playing before I decided to quit.
After all of the nerfs the Vector was actually pretty good because it wasn't altered while the other SMGs were all hammered by Treyarch.