Performance is sufficiently close to make it a preference call in my opinion. MP7 is usually placed immediately above the Vector in SMG tier lists, but some may prefer the Vector's irons or almost total lack of recoil.
Vector is better. Range difference is insignificant, but the difference in recoil pattern is huge.
What good is a gun that can't stay on target? MP7 recoil bounces horizontally and cannot be consistently controlled like the upward recoil of an MSMC/Skorp. And well the Vector recoil doesn't even exist so there is nothing to control.
MP7 has slightly better range, better reloading speed, and more ammo per magazine.
Vector has a bit better recoil and a nifty Select Fire if you have a fast enough trigger finger.
MP7 is better in the majority of situations. If you have a great trigger finger you could make the Vector better, but you'd have to be able to keep up that RoF constantly. --- And so begins a tale of vengeance and betrayal. Destiny by sinner sought. Tragedy by power wrought. Valkyrie Profile: Covenant of the Plume.