I would not choose between Deloitte and EY primarily based on which logo you think MBB will prefer later. The difference in brand value between the two is usually much smaller than the difference between a strong role and a weak role inside either firm.

Focus on the work you will actually do: strategy exposure, client interaction, analytical ownership, industry relevance, and how quickly you can build a record of strong performance. A role that gives you better stories and more responsibility will usually help more than a marginal difference in firm perception.

Team quality also matters because your first few years shape your development. A strong manager, good projects, and opportunities to own work can materially improve both your resume and your interview stories.

If the roles are genuinely similar, choose the one where you see the better learning environment and stronger project pipeline. You can build an MBB application from either.

I would pick the better team. Nobody at MBB is going to say EY was fine but Deloitte would have changed everything.

Project mix matters way more imo.