One thing to think about though is that bank loans might be variable rate, meaning it may jump up to a really high % interest in the future. Keep in mind that the loan probably won't be paid off for 10-15+ years so if it jumps up to a higher % than the Federal loans, that wouldn't be good.
Example: Loan % is 4 % for 3 years and then it can be varies from month to month from 2%-15%.