My experience with IRO has been great, anything i order from them is top notch quality and they have great customer service.
My brother inlaws 5.9 had the IRO steering, he loved it, was a night and day difference is steering slop and it seemed to be pretty beefy, It's an odd design (iro likes to be odd with alot of things) and the only negative i found was the joints were a little noisey (they squeeked)
I have no exp with Currie, but they ARE an industry leader in most of what they sell, with a cult that follows