Not sure what SOS rankings you are using but, here is the current strength of schedule with games played so far.
https://www.teamrankings.com/college-football/ranking/schedule-strength-by-other
UCF is at 43, while NU is at 64. I don't know how you can look at the opponents that both teams have played so far and think that NU has played a tougher schedule. Central Florida has handed Memphis and Maryland their only losses on the season, and UCF beat them both handily.
EDIT: Adding in the Sagarin rankings to show that UCF SOS is 65 in his rankings, with NU at 69.
http://sagarin.com/sports/cfsend.htm