It's not a matter of it being personal or not. The question is whether there is a security interest or not. A regular car loan, a title loan, a house mortgage, etc... all are secured by some property (a house, a car, whatever). The bank can come take the property (repo the car, foreclose on the house) if the loan is not paid. A payday loan, credit cards, registration loans, and most other debts are unsecured. There's nothing to back up the loan but the borrowers ability to pay.
Secured loans can have their rates dropped to the prime plus a few points (three I think). Unsecured loans can have their rates dropped to zero.

