Big Four Consulting vs. Underpaid M&A Intership

So I was offered this Analyst position at a Big Four firm for a consulting position - Information Technology in the FIG industry.

At the same time, I have an M&A internship offer at a BB bank, but it is underpaid with almost no opportunity to remain there after the internship period. The BB bank is operating as a branch in my country (deals are still all international) and has a fleet of recent graduated interns as their main workforce to minimize their cost structure. After the internship period ends they just recruit more and get rid of their current ones (top-performers get a place at their main branches but it is dependent on alot of different factors).

Three factors are influencing my decision right now: The money, the learning environment, and career prospects

My long-term goals are probably something related to IB and PE at a major european financial hub (i.e London) and so I was wondering what would be the best choice for me.

The Big Four position seems like the safe bet as money and career prospects are guaranteed within the company(although I kind of contradict myself saying I will shift to IB or PE at a later stage, but I feel like maybe they will adapt me better for my goals? I might be totally wrong on this one).

I am also not sure how much the position of an underpaid M&A intern at a small branch of the bank is worth, as I am pretty sure that:
1. there is no career progression within,
2. there is no contact with MDs,
3. will be doing small and support work for the "real" M&A teams in the main branches.

Thank you for reading.