The business cases are quite similar in all consulting companies. Just be aware that during Mckinsey interview you could face an "Interviewer Led" case, where the interviewer drives the candidate to the solution asking a lot of questions that have to be answered in a short time.
Another thing to take into consideration is that McKinsey is focused on financial services so it's more likely that your case will be about banking or similar. It would be good to have a base knowledge in order to better understand the case.