Whatever it was, the MSMC was absolutely insane on a local connection and dominated every other SMG easily. I'm not sure if the LANs I played at had the newest nerfs/patches installed so maybe it was the older version of the MSMC that I was using at the LANs I attended. The MSMC was definitely the best of the bunch on LAN though. So for a mid range SMG player like myself it was a useful weapon to have on backup if my MSMC wasn't doing it for me (never was a scorpion user and the Chicom/PDW got hammered hard as fuck by updates). The damage output was slightly low but every other SMG had their range nerfed, so beyond 30-40 feet the MSMC suffered greatly by that point in the game, while the Vector had it's range left untouched.

CQC to Mid only MP7 might edge him out though, if you don't plan on running those attachments. 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. MSMC eats most other SMGs he encounters, and he eats many ARs as well, provided you've got Barrel on him. 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.