Thanks, it really is a beautiful system. The exhaust guys I had install it locally, both of whom are older guys who have been custom making exhausts for American Muscle since the late 50s, commented on how nice and clean the design was and on the quality of the craftsmanship.
Regarding a comparison to the AA...Wow! That's a difficult question to answer! I haven't heard the AA....
From what I've read here's what I know. The AA has a higher pitched tone while the Gintani is deeper sounding. Gintani's system is a bit lighter. I think the Gintani is louder as well. Gintani has the best performance increase of any axle-back out there (again, based threads I've read and some dynos that a few folks did). But in all fairness I can't "prove" these things, and I haven't experienced them firsthand, I didn't run my own before/after dynos, so please consider the statements above subjective opinions.
There are guys on the forum who have had/heard both, and have personally experienced the performance differences, and hopefully one of them will chime in.