These are two completely different questions.
In "Tell me about yourself" you should be talking about your career path till now. You can finish this story with an argument about why consulting is the next logical career step.
I would recommend the following structure:
- Start with a 1 sentence summary of your background, why you are relevant for McKinsey and what's your unique selling point
- Talk about 3-4 of your roles (may be professional, education, extracurricular), 3 sentences each. The more experienced you are the more you should speak about professional roles. It can be also the distinct roles within the same organization. Typical structure: 1) What was the company 2) What you were responsible for 3) Greatest achievement in that role, that will stay in the memory of the interviewer (E.g. While working at Adidas supply chain I was personally responsible for the delivery of soccer balls to the Worldcup in Africa)
- The main reason why consulting (or McKinsey if you were a consultant before) is the next logical career step for you
“Why consulting?”, “Why McKinsey” or “Why BCG” questions are used to assess your motivation to be a consultant in general and to work in that particular firm. They will check how you have done your homework and what you’ve learned about them. They also want to make sure that you have a clear intention to work in consulting.
- The answers to these questions are supposed to be short and take no more than 30 seconds each.
- For each question, you should provide three bullets points with different reasons.
- Make sure that you guide the interviewer through your reasoning. Words like “The first reason”, “Moreover”, “Finally” will help you.
When answering “Why consulting” questions, provide three reasons why you want to pursue a career in a consulting firm. A general rule is to find the reasons that are important for you and logically fit everything you have done before (e.g. you want to grow further in financial services and get exposure to these clients). You can always use some personal rationale like your experience of working with consultants on a client side.
"Why this company" is a more specific question and can include the following arguments:
- The general marketing story the company is trying to sell (e.g. Bain is a small "Family" company)
- Brand / positioning / market share in the region
- More clients / projects / expertise in the industry you are interested in
- More well-known stories of success in your city
- Your friends working there
- Your interactions with the other consultants before the interview
- Your prior experience of working with the Firm on a client side
- Office traditions
- Work experience with firm alumni