good thing about a aum is that the map sensor, will allow the car to boost as is required. With a agu the boost level is set and thats it, nothing more.
i.e you have a k03s but you decide to fit a k04, the car will utilise the k04 due to the increased boost pressure, a agu wont even know its fitted and prob spike causing boost cut.
Several advantages to a aum but i still prefer my agu, personal preference though