I am in a large debate between the toxic r9 270x made by sapphire tech, and the gigabyte windforce 2gb rev 2 760. The price difference is like 10 dollars. I have had a 6850 for a few years and it's time to upgrade, which should i buy?
A question is how many games will you be play that will be using mantle?
BF4 jumps to mind as using it along with star citizen. the amd card will outperform the nvidia in those games... outside of that the 760 would be edging the r9 out.
would lean more towards the r9 right now honestly...
a very MINOR concern is if drivers don't get totally cleared out and a file decides to become a jerk, not as common as it seemingly used to be though.
Look up reviews for both cards and compare them against each other in the games you want to play and get the one that performs the best in those games.