260X or 270?

I am soon going to be building a new computer, I have done extensive research and almost come to a final decision. The only thing I have not decided on is the graphics card. I know that I am going to go the AMD route rather than Nvidia. The two cards I have been looking at are the AMD R7 260X and the AMD R9 270. There is only about a £30 difference between them but I am trying to keep the price as low as possible. Is there a big performance difference or should I just get the 260X and save the money for the AMD 300 series graphics cards (when they are released in the future)?

Many Thanks.

The 280 goes for $160. I'd do that.

I will look in to it thank you.