Which is better GTX 560 ti or HD 6950 or HD 7850

Hey! I'm looking forward to upgrading my VGA and my budget can only handle these cards GTX 560 TI , HD6950 7 HD 7850 because they are nearley the same price in my country N' I've really Checked lots of reviews for these cards but i found that the differences between them weren't similar in each review and of course I Wanna buy the best one from these 3 cards