save the headache, just get those Ibanez guitars with the original edge or the lo-pro edge :lol: .
if you like RG shaped Ibanez guitars, you die die also have to take edge pro. likewise for S series, if you like also die die have to take the ZR trem.
from what I see, you are picking a guitar based on its trem. thats...... quite a weird way to decide on a guitar. I mean, I thought the sound & feel should be more important than the trem itself. well, just my honest opinion.
alright, back to the topic. if I were to choose, I would say that the edge pro is smoother as compared to the ZR. however, the ZR would most definitely stay in tune better than the edge pro due to the technology etc etc.
super subjective issue I must say, there would be people who would claim the direct opposite is right.