The way I see it, you’ve got the original AUG, which is a great gun. It uses proprietary magazines, which sorta sucks except they’re great proprietary mags with a factory 42-round standard.
Then there’s the IWI Tavor SAR, the new kid on the block with caliber conversion kits in the works, lefty-friendly parts and that new gun smell that’s just awesome.
And finally, there’s the STG-E4, which like the Tavor, uses standard AR mags, doesn’t have caliber conversion kits, but does have a quick-change barrel system with 300 BLK barrels in the works. Also, it’s usually the lowest-priced.