Lots of choices, get what you like
I have shot them all and own a Uzi. Parts and mags. are cheap, the gun is very well built. If you ever get an out of battery incident, the Uzi protects the shooter the best and oftern the gun is still good to go or just replace the top cover. One can do all kinds of things with an Uzi including easily mounting a suppressor and optics if wanting to do so. The Uzi in stock form is almost as compact as a mac. but one can install the wood stock and other goodies to make it bigger. If the gun is a registered reciever gun rather than a registered bolt gun, you can change calibers to 22 or 45 if desired.
The 76 is very nice shooting also but only one person makes parts for it should it need it. I too love the rate of fire and to myself it has the feel of what a subgun should be.
The mac really was transformed with Richard Lage's uppers. Others started slowing down the mac but his items appeared to trump them all. His converted guns are now placing in the top spots at the national Knob Creek subgun matches. I have only fired a stock mac and prefered the slower guns to a stock mac but again Lage's uppers have transformed the guns. And Richard is a really nice guy. Mac's lingered long in the 2.5-3K range prior to the lage upper, now they are creeking up.
If you can fire them before buying, by all means do so.