To me, though, the manual of arms with no bolt hold open feature and because the trigger really kind of stinks out of the box and to me it seems like working the bolt is harder. Thus, the scorpion is for me.
HK solved that with the UMP.
True, but they 'gave up' the roller delayed advantage - hence why I believe the Scorpion is such a good deal.
And unless you buy in to the 'your gun's gonna blow up son' its a great buy.
I can tell you, having handled a real HK and a $1500 clone I found the bolt stiff to actuate and coupled with the fact that you MUST lock it back PRIOR to the mag change, I did not like it. Also, the trigger is easier to make very good to excellent on the Scoprion for peanuts AND the safety is a ton easier to make right.
Then there are the magazines. The CZ has the best combination of reliability/ease of loading (curved design) and cost.
So while I was serious about liking the MP5, I'd rate the Scorpion better for most folks.