They both have their pros and cons. What finally sold me on the IOR was the NF's occ lens rotates with the Butler caps in tow. In other words, when turning the power ring up/down the Butler caps rotate with it. To me, very annoying.
The biggest downfall about the IOR 3-18x42mm I have is it's heavy /ubbthreads/images/graemlins/frown.gif. Every single piece of spec sheet material I could read on it says 22 oz. Mine must have lots of "LEADED" glass because it weighs 29 oz. /ubbthreads/images/graemlins/mad.gif
I looked hard at the 4-14x50 but was sold over by the 3-18x42, especially once I got my hands on it.
I've handled NF's, they just didn't trip my trigger.
With a 20 MOA base on my Rem 700, the 30-06 Ackley w/ 180 BT's at 3050 fps can still get to 1540 yds in the IOR.