The general understanding is that Bain - interviewee led, Mck, BCG - interviewer-led. However, it varies with the interviewer and even at McKinsey partners in the later rounds can give you an interviewer-led case
It may seem for you that these 2 types of cases are different, however, the interviewer-led type is just a simplified version of the interviewee-led case. My advice is to always prepare in interviewee-led format so that you could solve both easily.
What to expect:
- Engagement managers (1st round interviews if you think of phone interview as round 0) generally use Mck casebooks and most commonly make interviewer-led interviews. In this case they ask you a) To make a structure (issue tree) b) to drill down in some branch of your structure and calculate something. Or they may even ask to analyze smth unrelated to the structure c) question on creativity (e,g, list 10 ways to increase revenues). However, you should be ready for both type of interviews at this point
- Partners and directors have their own favorite cases and mainly want you to lead. The key difference:
- You ask clarifying questions in the beginning and make a structure
- You lead the case through the structure you've prepared a) asking questions and trying to identify the root cause of the problem in the branch of your structure b) making a transition to the next branch c) proactively calculating the data and making data-driven conclusion from the data they give you d) Making a conclusion when they ask you to finish a case