IMHO, no contest: take the student loan. A Stafford loan, not a personal loan. If he takes out the student loan now, he will not have to pay on it until 6 months after he stops attending school at least part-time. That means any extra money he makes working from now until graduation can be saved up to pay on that loan. If he is eligible for a subsidized loan, he won't even have to pay any interest on the loan while he's still in school. If he is eligible for only an unsubsidized loan, it will accrue interest while he's in school, but he can make it less painful by paying that interest amount while he's in school and still save money towards paying off his loan principle.
As a PP stated, any interest he pays on that loan is also tax deductible. And make sure he claims his school expenses on his taxes, as it really helps (DH's tuition always helped us get quite a nice chunk back on our taxes).
While car loans are very seldom flexible if something happens, a stafford loan can be deferred if you go back to school, sometimes for a short time if you have a financial hardship, and they will often work with you to arrange easier payments (graduated payment, income sensitive, etc). You really won't get that with a car loan.
One caveat, however: student loan people WILL garnish your wages if you don't pay, and I'm fairly certain they aren't eligible for adjustment in bankruptcy.
I am VERY grateful for the student loans DH and I were able to take out, as we would not have been able to go back to school without them. The loan people at our individual schools and our lenders have been nothing but wonderful and very helpful. But, as with any financial thing, the first step is to be an informed borrower. Way too many students take out loans without the first clue what it means and what is expected of them. Overall, knowing what I know, I would go with the student loan.
Hope that helps!