IPhone 5c or 5s. Which would be the better buy?

I know I want to upgrade in the future but which would be the better but?

Right now I have the iPhone 4 and would love to upgrade by my birthday (which is one year after I got the 4)

Oh god. Get the iPhone 5s. The iPhone 5c is just an iPhone 5 with a cheapy plastic back. IPhone 5crap

IPhone 5s

IPhone 5s. IPhone 5c doesn't look nice and isn't much cheaper. Besides, if you decide to buy iPhone 5c, why didn't you buy iPhone 5 last year? The spec is same.