It completely depends on the situation.
Psychologically speaking we seek things that we need before we seek what we want, according to Maslow.
However, we are not bound solely by reason.
Which would explain why I would most certainly go hungry for a week if I could have something I really wanted, like twenty books on my wish list.
People choose what they want over what they need all the time. That's why there's a huge debt crisis in the world. People want what they want when they want it. And that's usually right now.