I hate to say this but Ferentz has done a top notch job at Iowa. Just like McCarney did a top notch at ISU. Both these guys did more with much less. More impressive than any NC at those top notch programs.
McCarney started with nothing and made ISU better.
Fry started with nothing and made Iowa better.
Ferentz started with a program built by Hayden Fry and made it worse:
Overall Iowa Record:
Fry: 143-89-6 .613
Ferentz: 70-53 .569
Big 10 Record:
Fry: 98-61-5 .613
Ferentz: 43-37 .538
By your logic, Hayden Fry did a top notch job at Iowa (which I agree with), but not Ferentz.