The worst student loans to get away from are the gov't loans. If you declare bankruptcy at any time, non-gov't loans can be included in the resolution, but your gov't student loans cannot be.
They're a more permanent and unforgiving type of loan, and of course, they're the most reliably easy loans to get approved, so most students use them.

It's a bit of a racket, IMO, but I needed the money they were offering and I accepted the terms of their loan, so I'm stuck with it.