AX1500i equivalent to the Superflowers? I'd say it surpasses them.
Anyway its all debatable. We're comparing excellent PSU's with excellent PSU's. To say one is hands down better is again debatable. In my humble opinion of course.
JohnnyGuru's review of the SF 1600W and the AX1500i put them very close.
I say this as someone that has an AX1500i!