There are many university ranking consultancies trying to compare one leading maths department with another and to conclude which one is better. Although this doesn't seem to be a very reasonable thing to do (since you cannot compare apples and oranges), many high school students still see such ranking as an important factor when deciding where to go. An example of ranking can be found here.
My question is: why, for example, is MIT placed above Oxford (and many other examples) in most rankings? Although different organisations give vastly different rankings, MIT seems to be always above Oxford. Is there any real difference between their undergraduate education or is it just that the criteria of rankings are unfair? (NB DO NOT focus too much on MIT and Oxford; they are just examples.)
I'd like to limit the discussion to undergraduate education only: does such ranking really help when choosing which college to go to? Also, be aware that I am NOT talking about the overall ranking of universities; I am just talking about the ranking of math departments.
I believe this question is not very opinion-based - it can be answered objectively by a detailed examination of the course contents and teaching methods, and how those are related to rankings.
I am aware that those rankings are not solely about undergraduate teaching, but chances are that high school students care about the rankings more than anyone else.
To summarise, are rankings helpful in assessing the relative merits of undergraduate education at the maths department of different institutions?