I've got a fair amount of experience with MP5's and a Micro-Uzi FA.
I see the Uzi as an extreme CQB weapon. The open bolt can be, confusing, if you're not used to it and you aren't paying attention. It does keep the weapon coller however, and allows for a higher rate of fire.
MP5's are more versatile in my opinion, and easier to fire accurately.
If you're handing them out to your guards I would give it to whoever your most safety conscious/fire disciplined is. They're VERY easy to empty before you know it.