New aluminum MacBook or white MacBook – which is better?

I'm thinking of buying a macbook. But it is hard to choose between the new aluminum one or the white plastic one. I not exactly just choosing according to the design, but also the performance. The old one is much cheaper and the aluminum is more expensive. I really want the aluminum one but it is expensive. But I want the best for me even though it is expensive. So I really need your help. Thanks!