i would go with 760 because for extra 40 bucks more u get higher overall performance in other way the 760 will last longer than 270 , as for mantle when proves it's effective on games as on theory but for now 760 is Superior
The 270 is $70 or more cheaper than the 760, to a lot of people $70 is a lot of money. And the 270 when overclocked is just about a 270x, which is just about a 760, for $70 less. Plus, Mantle will only help the 270. And of course the 760 is superior, it is also more expensive.
He wanted in the SAME price range, not something that costs 50% more than what he was looking to spend.