It would greatly depend on which IOR scope you are comparing to the NF.
I like my IOR 4-14x 50 Tact
much better than the NF 3.5-15. Particularly in low light conditions it's the single best piece of glass I've ever owned or shot. I've used it on coyotes on a full moon night without any added illumination out to 500yds on wheat fields.
I like my IOR 6-24x50 35mm tube
better than the NF 5.5-22x56 I compared it to. Again outstanding in low light, and much better in extremely bright conditions than either the NF or Mark 4's and VXII Leupold's I own.
I'm not a man of wealth by any means and my next scope will be the new 4-28x56mm 40mm tube IOR
I haven't shot the latter yet but I have had an opportunity to play with one a bit in both bright and low light and it's phenomenal. The incredible 85 MOA range of adjustment makes it a tremendous Long or extreme long range optic as do the 1/4MOA click values.
High end scopes are like high end vehicles or rifles though and a lot of it just boils down to personal preference. Some of it too depends on the individual users eyes and light sensitivity.
I have a problelm in extremely bright light but I have exceptional night vision and always have had this as an issue. In both extremes I really love the IOR's better than anything else I have owned or tried.