having worked at 2nd tier firm (ATKearney) and largely discussed with friends at MBB, you'll find below my personal opinion:
- you'll still learn a lot at 2nd tier firms, and will evolve in very demanding and challenging environment
- nature of jobs are similar, even tought sometime MBB get more prestigious engagement, in the end all this firms are mostly competing for the clients and jobs
- difference in people working there are not as big as we could think. A key point to consider is that most partners are transfering from firm to firm depending on their personal interest. And sometime they transfer with their full team (principal, manager, associates).
- MBB will for sure offer more structure in daily work (larger internal expert network, more methodology develop) vs. more entrepreneurial / self driven engagement methodology in 2nd tier firm
- MBB will for sur offer better personal development perspectives beyon the job itself : higher global exposure, better training programs, exit opportunities