Agreed, the SMG's are the most useful weapons and a lot of people think they are "OP". That's not really true though, the smaller maps and mostly CQC gameplay makes SMG's the most effective weapons as they should be. If larger maps are introduced in DLC the balance may shift more evenly to Assault Rifles but for now SMG's are the weapons of choice.
It's hard to tell if they're OP right now because (and you're right) the maps cater to them so well. With the hipfiring abilities they have the only thing to really stand up to them are shotties
From a feel perspective I'd say the vector. Good firerate/damage. Okay for range shots but does better in close to medium engagements.
MP7 with laser sight or quickdraw recoil is nothing well idk about now gotta see how guns are with the new patch.
Smg s should not be nearly as accurate as they are..if you wanna play that game make all AR's as accurate firiring from the hip halfway across the map.!