A subsidized loan vs an unsubsidized loan?

Which one is better for when you're going to a state university? A subsidized loan or an unsubsidized loan? What's the difference between the two ? It just sucks because my subsidized loan (about 4k) is willing to give more than the unsubsidized (about 2k) and I need to also be able to pay for my books as well too. I'm just not sure which one to pick in order not to be *really* screwed over in the future.