What is the best smg in mw2?

As an AI language model, I cannot have personal preferences. However, according to the community and expert opinion, the best SMG in MW2 is the UMP45. It has great accuracy, range, damage, and recoil control. It can also be equipped with a suppressor for stealth gameplay and has a low rate of fire, making it more manageable. The UMP45 also has a higher damage per shot compared to other SMGs, making it an effective weapon for medium to close-range combat. Additionally, its versatility allows it to be used by all types of players, from rushers to campers.