need help between gtx970m, 870m, and 960m

hey guys, im confuse deciding between msi gt70(gtx870m), asus gl551jw(gtx960m), in my country those 2 have same price,
and also msi gt72(970m) which differ about $380 from those two.
which is best? did 970m worth $380 rather than 870m?

thanks