Hi,
If you are talking about FIT interview and Why BCG question, I would switch from BCG vs McKinsey question to Why BCG particular office?. Arguments may be:
- More clients / projects / expertise in the industry you are interested in
- More well-known stories of success
- Your friends working there
- Your interactions with the other consultants before the interview
- Your prior experience of working with BCG on a client side
- Office traditions
etc.
Best