Internship at a credit union vs. regional bank

Due to my mediocre GPA (3.1) I was turned down for internships at the large bulge bracket banks. As investment banking or corporate finance are my two passions, I want to have good experience entering those career paths. I need your help with a decision... I have the chance to intern at my regional Federal Credit Union as a credit analyst. Although it is not a larger bank or glamorous internship, I will be learning valuable skills by doing efficiency analysis, credit ratios, and excel projects. I also was offered a position at a large regional bank accepting calls from customers who have questions about our new bank wide overdraft policy. Although it is not directly related to finance, I think the experience would provide me with sharper sales and customer relation skills as well as the name of a publicly traded bank on my resume. Which summer position would be better experience before applying for entry level jobs my senior year? Thanks for your help.