Need advice asap please! M&A boutique offer vs. BB assessment center

Hi guys,

I'm facing a fairly tough decision right now and was wondering if anyone in this forum could help me in coming to a good solution.

So I'm from a European non-target and recently secured an offer from an M&A boutique (Frankfurt) for an internship from April to June next year and am incredibly happy about that. But now I'd still have time for another internship from January to March and also secured an offer from another reputable M&A boutique(Frankfurt) for that time, which runs out on 23rd October. I am also invited to the assessment center at BB (also for an internship from January - March; London office), but it's only one week later.

What do you think I should do? Take the offer and do two back-to-back M&A boutique internships in Frankfurt or not take the offer, go to BB's assessment center and hope that I get the internship there?

Any help or insight is highly appreciated!! Thanks in advance.