I'd like to buy an Ibanez S series guitar soon, and have narrowed it down to these three models-

S520ex - $500 (22 fret, black)
S570b - $565 (24 fret, white)
S420 - $480 (24 fret, weathered black (stained))

the S520ex looks to be last years model, but possibly has the nicest finish, and the coolest fretboard, as well as covered pickups, but only 22 frets, compared to this years models.

Would there be any difference in the ZR trem between last years (S520ex) and this years models?

Does anyone have experience with the S520ex? would it be a better buy than this years 24 fretter S's?