It depends on your income and your expectation of future income. These choices often come up in student loans. If you come out say, for example, as a social worker and your expected annual income is going to start off as $15,000 and not rise above $30,000-$35,000 you might take the graduated. But if you are graduating from medical school as a neurosurgeon, you might want the flat rate because while you won't make much while in your residency, once you are on your own and can call your own fees and driving a Porshe, you won't want something based on your income.
