That is a very difficult question to answer because everyone could define "better teams" differently. If you define the quality of the team by their end-of-season record then Iowa beat a better MSU team last year.
But there are problems with defining teams that way: if you beat almost everyone, then no one was better than you by that metric. For instance, the 2009 Penn State team the Hawks beat in Happy Valley finished with the exact same record as the Hawks and beat LSU in a bowl. But because the Hawks finished 11-2 you might not say they beat a better PSU team. However, had Iowa lost to Minnesota that year, then PSU would have the better record and you could say that Iowa beat a better team.
Or do you define the quality of the team by the recruiting rankings? If so, Iowa beats better teams all the time. However, ultimately the coaches are responsible for the players that are on the team, so that metric is also flawed.
Or do you define the quality of the team by the amount of NFL talent? This is also somewhat flawed. Iowa develops a ton of NFL talent due to their pro-style schemes and their emphasis on thinking on the football field. Thus, their players are not necessarily more talented than their opponents, they are just more pro-ready.
Ultimately I think you judge a coach by wins and losses, opponent be damned. Enjoy a win no matter who it is against, and accept that losing is a part of sports, no matter who the opponent.
As to your premise that the Hawks have gotten very good at losing to less talented teams under Ferentz, consider the following numbers (first 2 years of both coach's tenures and last 2 years of Fry's tenure ignored):
- Ferentz has a better winning percentage vs. the Gophers than Fry, and the Gophers have won at a 48% clip overall during Ferentz's time, while only a 38% clip overall during Fry's time.
- Fry beat NW consistently (14-2), but the Wildcats won 28% of their games during his tenure, and did not make a bowl until his last 2 years. NW has won 50% of its games in Ferentz's tenure and has made 6 bowls (now eligible for a 7th). NW also has a winning record vs. Wisconsin during this time.
- To Fry's credit, he dominated ISU and Wisconsin. Both of these teams have been considerably better during Ferentz's tenure than during Fry's, but he still owned them both.
- Ferentz has a winning record vs. every Big Ten team save NW and Ohio State during this time span
