AEM is awesome as long as it's a v2 or infinity system. The v1 boxes do the trick, but have far less adjustability.
I run a v2 box on my 500whp e85 240sx. It's a great system, and has full flex fuel capability which I use. My only gripe is the accel enrichment and delta tables are only good up to a certain point depending on theottle body size, and intake plenum volume. But on a Busa I don't see that being an issue at all.
I'd look in to the holley efi hp box. It's 1300, and does everything that $3200 motec can do. Mps has a plug and play harness for the Busa. We will be installing this system on an upcoming grudge bike build. I also have a Holley efi system on my big single turbo LS mustang. Stupid easy to use, and I would suggest it to anyone making a jump to a first time stand alone. You literally have to try to blow your stuff up with the Holley system.
The motecs can be very overwealming. Not saying you can't learn it, but it's very advanced. I really like pro efi, also doing one of those on a bike now. Great software, but it's stupid expensive.