The diffference, like it says on the website, is pretty much an integrated trigger guard (I'm pretty indifferent about this, altho it IS a stronger solution than a regular seperate trigger guard, but broken trigger guards are unheard of), it does however prevent a 200lbs gorilla with a hammer from breaking one of the lower receiver trigger guard ears during the trigger guard roll pin installation on a regular lower, it has an enlarged magwell to theorically insert mags more easily, and a threaded bolt catch pin instead of a roll pin (I'm also indifferent about this), and an upper receiver tensioning screw that serves no functional purpose besides wearing the rear takedown pin holes at an accelerated rate. Functionally speaking, identical to the basic lower. It's just user preference at this point.
IMHO, it's not worth the extra, but that's just my opinion. They're sold out tho...