It comes down to this: I believe Iowa is superior to Northwestern. But the line is short here because Iowa wasn't sharp in an opening-week loss to Purdue while Northwestern crushed Maryland.
Now the Wildcats are stepping way up in class here and they're doing it in Iowa City. 
Iowa's new QB Spencer Petras is going to get better. The Hawkeyees were breaking in a lot of new faces at Purdue. Iowa has the best running back in Tyler Goodson and their defense will prove far more challenging for Northwestern than Maryland's did.