At your high income level, I think the traditional pre-tax will almost certainly be the better choice, both now and after your loans are paid off. The basic rule of thumb is, use the traditional if you expect your income to be lower in retirement than it is now, use the Roth if the reverse is true.
In your circumstance, what I'd do is max the trad 403b, build a small emergency fund if you don't have one already, then direct your excess savings toward the 5.6% loan. With your income and no family to support, you should be able to pay off all the loans in a few years, all while saving for retirement. Good luck!