Radeon 6870 or gtx 560 ti??

Well i am building myself a new system and i already order some parts my cpu is a phenom ii x4 965 ( i went with AMD cause it made it $100 cheaper and it still had a good performance) i have a Corsair 600w building series PSU 8GB of ripjaw series and my MOBO is asus m5a97. thats what i have so far. and i know all the other parts im gonna buy i just dont know what GPU to go with.. i am on a budget so i was gonna go with

radeon 6870
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

but i am really wanting to play arma 2 max settings (besides view distance and AA) and i want to play arma 3 when i comes out on high and i was thinking would this card

gtx 560 ti
http://www.newegg.com/Product/Product.aspx?Item=N82E168...

is the gtx 560 ti worth the like $60 difference? especially for games like arma 2 and 3?

but i am leaning more toward the 6870 i dont wanna spent the $60 more unless its a huge difference.. thanks!