EY Complex Security Summer Intern vs BAML S&T Rate Option Summer Associate

I'm seeking advice on EY's Complex Security Summer Intern vs BAML's S&T Rate Option Summer Associate. I think both companies have friendly culture. They are both located in NYC. In EY it seems I could get exposure to broader asset classes from stock options to fixed income securities and different types of loans but in BAML I was assigned to the rate option desk only. However, in BAML I could be a summer associate but not a summer analyst, and BAML is a BB which might be a better place to start my career (provide better training, big names, talented colleagues,...). Another point is I have accepted the offer from EY a month ago so I'm worried I would be on the Black List if I decline the offer now. I appreciate your suggestions. Thank you~