You know there's a world of difference between the two, judging by your screenname.
Depends, if you want stealth, the MP5SD5 is quieter than a CAR-15 with a silencer.
Anyway, they still use UZIs rather than the superior MP5s (or Mini UZIs instead of MP5ks), which they've done for years.
They really try to use their own weapons, and try especially hard to avoid German ones.