Chrome Book or Surface RT?

So my MacBook Air just died on me and the cost of replacing everything that is wrong with it is just too much. It's been a fantastic road warrior but now I need to get something to take its place. So I was looking at a Surface RT or a Chrome Book. Budget is small (under 500) and I want to keep it light and fast. My needs have only been word processing and web browsing. Though I am concerned with lack of iTunes on both machines (my ipod shuffle syncs). So I am looking for thoughts about what each platforms advantages and disadvantages are. Also, if anyone has any other alternatives to these 2 options that would be good as well. I should note that I am not in a rush and can wait it out for a month or two if need be. Any thoughts would be greatly appreciated.