I own both guns but it would be hard for me to say which is a better fit for you.
What other machineguns do you already own (assume you own others being a SOT), what access to ranges do you have (i.e. can you shoot rifle caliber guns as easily as subguns), and do you have a preference for subguns over rifle caliber guns or vis versa.
Personally for me I would choose the HK33 over the Uzi, but I also am not really a very big Uzi fan (understanding that I am in the minority in this option) and am sort of an HK junkie myself.
I also prefer rifle caliber guns over subguns in general as well, but again that just me.
If I was an SOT and had access to presamples I would definitely buy another presample HK33 and swap or cut the barrel to make it an HK33K which is one of m favorite rifle caliber machineguns. I wouldnt personally bother to buy another presample Uzi as I don't shoot the transferable one I own much to begin with.