Kill and Hazell field teams not as prone to as many OL illegal procedure penalties, neither has players with turnover issues like NU, neither have teams that prior to the snap look lost, confused, not aware of their assignments and looking to each other and the sidelines for help as to assignments. Their teams do not have these coaching problems (like NU does). Now... they have lesser players to work with and perform less well than do the Huskers as a result... but not for coaching issues.... but talent issues.
The lack of obvious coaching problems at Minnesota and at Purdue relative to the obvious coaching problems at NU make me think that Kill and Hazell are, for their part, at least as good... and likely better than Bo. Neither have the context to recruit like the Huskers do... so that I have left out of the discussion. I simply look at team game preparedness (unresolved continual problems, confusion, turnovers, penalties, losing focus and giving up huge #ers w/o responding in real time to stop the bleeding, etc.) and NU has more problems in that regard than most teams --- and that is, at least largely, a coaching thing.
You ask for unbiased... well simply look at the Huskers on the field and you will see many things that the coaches need to fix... the Huskers, as much as I love them and have for 30 years followed them, are of late really undisciplined and have all sorts of fundamental issues to iron out... they do have talent and (at times) play with some real heart.. but there are undeniable coaching issues that transcend those at most places. I do not see those problems as obviously manifest at Minnesote or Purdue (though, admittedly, I have seen each team only several times a year... and so the sample size is small and the assessment anecdotal... but from what I have seen, I have not seen the same level of problems seen at NU).