I also have a Steel Storm, which uses TWO CO2 capsules, and shoots either semi, or 6-shot bursts.
I must say, the Uzi "feels" more authentic (I think - I've never fired one, lol), but it strips down cool, and has noticeable "recoil". But it DOES chew through CO2 on FA...maybe 2 mags of 30 BBs and you're done. Of course, firing in shorter bursts, and giving the powerlet a minute to warm up again, will increase life. Semi-auto provides the longest life...but, hey...
The Steel Storm is probably a little better "value" at closer to $100-$125, but it is more plastic than the UZI which, to ME, feels and looks pretty authentic!
The Steel Storm DEFINITELY hits a little harder as well, the UZI using up a lot of CO2 to work the "action".