Its actually all about feel. How smooth the trem is.
For Ibanez, the smoothest is still the original Edge. Then Lo Pro Edge, then Edge Pro.
Another thing is reliability... you still see Ibanez guitars with Edges from back in the early 90s ... same for the Lo Pro... its got repute. The Edge Pro is still relatively new.
And I can't stand the fact that most Edge Pros are cosmo coloured. The cosmo finish rubs off the fastest, its the weakest finish. Why can't more Chrome Edge pros (ala JS1200) or Black Edge Pros be made?!