The only things I didn't like about the SMGs, was you practically pulled the trigger, and then you were out of ammo very fast. I've never looked, but I was wondering if it was easy to find mags for em nowadays. ( For M11 styles of course).
Second, it was difficult with the models that floated around D-9, was being too hot to use as CQB grade, or side arms.
I think Metal wound up with the only one that could be shot indoors. (Then, not having a SEMI option, made it difficult to use in SOGOs, cause we hardly get to use burst fire there. )
Other than that, I like the style of em... especially when not doing regular "army" types of scenarios... "drug dealers" and "mafia hit men", maybe "Thugs", types of "characters" , those weapons really fit that type of persona very well.
I think if I got SMG... I'd like the Tech-9s , that KWA promised to make, but have yet to see that actually come to pass... , but I'd most likely go with the MP9 or MP7 varieties, they simply have more options in the current markets.