This is a good question. The short answer is both matter. However, it’s important to understand how MBB approach University recruiting. Having led both Office, Regional and University (MIT Sloan) recruiting as a Partner at McKinsey, I was often times of asked why McKinsey recruited at certain schools and not others. The answer actually comes down to a combination of factors. But, the main factor is the # of quality candidates available from a particular University. Scale matters. While the top 5 candidates at University X may be just as good as the top 5 candidates at University Y, the top 50 candidates may not be as good. So, there are typically a group of Tier 1 and Tier 2 Universities for both Undergrad/Grad and MBA recruiting. The difference being that Tier 1 Universities have full time recruiters assigned to them where a single recruiter may cover 4 or 5 Tier 2 Universities.
So, the primary factor for MBBs is the University and the second factor is the GPA, especially for undergrads. For many MBA programs, you don’t even disclose your GPA. This is not to say that GPA does not matter. There is an minimum GPA or ‘ante’ if you will. But, it’s a bit like your SAT / GRE / GMAT score. As long as it meets the minimum, you are pass the bar. However, there is a little extra credit given for honors / awards / distinctive GPAs.