AXIA variants

[Whitewolf]

What's the diff between an AXIA with an Y in the third line and an AXIA with an 9 in the same line. I've got a 9. Which is the best? Are there any other AXIA's

 

[Biggs]

I read in some site once that the majority of the ones with the Y had the max overclock of 1400Mhz while the 9 reached 1450Mhz.