All of the SMG's are adequite with identical impacts on your runnings speed. UMP is the best for damage and would be my recomendation along with the Mini-Uzi with a silencer or rapid-fire it seems to have amazing range with enough bullets in the clip for multiple enemies.
If you are rushing be sure to use Marathon(Pro) Lightwieght(Pro) and Ninja(Pro)/Commando.
These are the best technical options.
A.K.