Not a 'sensible' choice of guns. It's going to be hard to get mags and parts. The only reason anyone gets a gun like that is that they love it. The 'sensible' sub machine gun would be an MP5. But who wants to be sensible right?
Too expensive...personally don't think it looks as nice as people make out. It's quite cool and futuristic but as Russ said, not really practical. Unless you have a lot to spend I would rather get a good MP5 too.