I vote UZI. I own a Group/Vector full-size, have had it for over 20 years. I had a m11/9 and sold it. Shot plenty of Laged out MACs and while nice, they don’t do it for me as a collector. The Uzi does it for me as a collector and a shooter. It’s not flexible like a MAC, but I don’t care. I have an M16 and HK sears for flexibility. I appreciate the Uzi for what it is, an iconic SMG that’s a great shooter in its own right with inexpensive widely available mags and (at least for now) good availability of spare parts.
It really comes down to what YOU want. Do you have the ability to buy more MGs in the future? Are you a collector, a shooter, or both? If you will only own one and want maximum flexibility, the MAC is it.