And it's not one you'd expect!
There are a lot of ways to assess the best university for you, such as reading about the university, talking to students, and visiting on open days. I'm going to give you another possibility in narrowing your search. I've sorted through pages of figures from Unistats showing which institutions are leading to the highest-paying jobs after completing your first full-time degree.
In the table below, look down the list of subjects in the first column for courses you're interested in. The second column will tell you which universities appear to lead to higher-paying jobs for students taking those courses. The third and fourth columns give you the average salaries students have got afterwards, and the fifth column tells you how this compares to other universities, and what range of salaries you might expect in general:
Salary after completing first full-time degree
These numbers just represent either one or two years of aggregate data. Institutions with smaller classes might skew the results even more, so we cannot yet know how reliable this is for the future. However, it makes a potential starting point and it'll get more accurate as I develop it in the years ahead to build up a bigger and more accurate picture.
The six month figures (third column) from Unistats are based on actual earnings from students attending the institution.
The 40-month figures (fourth column) are not available by institution. Instead, these are regionally-adjusted sector averages based on where graduates from that university normally go to work. This probably explains many of the weird results (and probable errors) such as nursing students at City University apparently getting paid less after 40 months than after six months.
Also, the subjects are loosely classified, which is why you have the University Of The Arts in London competing with London Metropolitan University on management studies. The former university will presumably be focusing on fashion, publishing and so on.
The top universities
Some of the most respected universities are only top in a few subjects. Oxford comes top four times, Cambridge twice, Kings College London once, and Imperial College London three times. This is probably due to the narrow focus that many universities have, as well as competition and the universities' links with employers. Even so, two to four appearances at the top is more than most universities.
Meanwhile, Kingston University is the overall winner, appearing seven times with the highest salaries in civil engineering, building, sociology, law, business studies, accounting and design studies.
On the whole, differences in salaries are smaller than I thought, although that doesn't mean you should be complacent in which university you choose. The universities that appear to lead to better jobs are typically getting you at least £4,000 more than the worst universities after just three years.