I remember someone complaining once about the mag release on the AUG, saying that it makes mag changes a bitch, but I forget who it was. Watch this video and tell me you can't do a fast mag change with an AUG. You may need to add a little weight to your airsoft mags inside the base plate to make sure they drop but it works for me.
Steyr AUG A3 SA/USA Bullpup Demo (4min) - YouTube