MSCI ESG Research Analyst VS Deloitte Audit

Dear all, I need career advice.
I am a penultimate year student looking for an investment banking career. This year I got summer intern interviews from several banks, but I'm not sure I would get an ideal offer this year. So there is a large possibility I would apply for graduate programs next year.
And recently I got two offers for winter internship. One is doing ESG research at MSCI. ESG represents for environmental, social and governmental issues of companies. And another is doing auditing at Deloitte.
Both offers have their advantages and disadvantages. MSCI is a prominent company, once affiliated to Morgan Stanley, One of my interviews currently going on is from MS. If failed, I would definitely apply again next year. MSCI experience might add to my resume? But doing ESG research might be dull and would not add to my deal sense. On the other hand, auditing might give me more deal exposure. I have not done auditing before, (I have got an IBD internship on my resume).
Which experience would add more to my resume when applying for IBD?
Many thanks!