I'd say the biggest functional difference are the larger opening in the receiver for the ejection port (makes feeding a single cartridge in by hand easier), the change in the way the magazine is removed (harder to accidentally drop the mag out on an A7) and the safety / bolt release (you can open the bolt with the safety on, if desired). The other changes like a thicker receiver in the A7, the metal feed lips on the mag and others have there merits, but don't really impact the day to day use.
Both mine shoot equally well, feed smoothly and have great triggers.