Yes, I've seen (and loved) Azu, though I didn't review her since that took place while still banned.
The better ass? Well, that would depend on taste... no pun intended.
Azu's buns are f'ing gorgeous, and I couldn't get enough of them. But they have 2 very different bodies. Azu is a shrimp (an incredibly beautiful, sexy shrimp, but still a shrimp) in comparison, as Eri is a tall/large girl. If size matters... Eri's booty totally eclipses Azu's, but I imagine some would prefer the wonderful (though more modest) buns of Azu. As said in the review. Eri's ass is not for the faint of heart!
All said and done... I want to repeat with Azu before Eri. As great a time as I had with the latter, I had an even better all around time with the former.