Can't go wrong with either really, all dependent upon previous maintenance history and condition.
However, I would try to find a car that is safetied or from an owner willing to do so.
If not, you could end up being stuck with a huge repair bill you were not aware of.
If not willing to safety, ask if they are okay taking it to a shop for an inspection. That way, you pay the bill, but at least you can know of any hidden issues, and possibly negotiate a deal.