http://forum.square-enix.com/ffxiv/threads/31781
The arguement used to justify this change is that it will improve usability and balance. Players will have more freedom equipping accessories.
I found this very confusing when you consider the actual measures taken:
Yes slot costs are being removed, but the number of slots goes down from 9 to 5. This basically means that there hasn't really been changed anything at all when it comes to the amount of stats.
When it comes to picking the stats, freedom is actually taken away from us! It's pretty obvious that certain item slot types will get certain stats (not much different from the materia system), but with the slots going down from 9-5 you can't focus on your favourite stat. Tanks, for example, can't focus on taking double wristlets anymore for a health, defense boost
Focussing a bit more on the balance part: The effects of stats on gear with the exception of mp and hp are hardly noticeable at all. SE is worried that melee doing one more damage from extra Strenght will bring the game out of balance?
I can understand the simplification though. It's less data to worry about, but from a players point of view: it's a loss.