As others have said, the MP5 is easier to shoot, but the PDW is sexier. Both were reliable IME.
I never liked the telescoping stock, so if I had an MP5 it would have the non-telescoping stock.
In case you're ever tempted, the 0-1-3-Full trigger group makes a bad selector even worse.
Circa late 1990s, I watched a guy at an USPSA match run a .38 Super with an optic and I wondered why we were still using MP5s. Fast forward twenty years and if I wanted to conceal a 9mm with a lot of rounds, it would be a G34/RMR, not a PDW. You don't have a practical need for PDW even if there is a practical use for one. That's OK. 'Murica. Buy the MP5 and get your Diehard on.