What about memory bandwidth, 970 is 256bit vs 1060 192bit ? i assume not important in this case
That doesn't matter that much, because NVidia has improved the
delta color compression algorithm.
Just an example:: The GTX 970 even beats the GTX 780, despite the higher Memory bus/Interface Width, which is
384-bit, on the GTX 780, and also 288.4 Memory Bandwidth (GB/sec).
Nvidia, actually did a great job with the MAXWELL and above GPU series. One of the major improvements Maxwell makes to the GPU architecture is a third-generation
color compression algorithm, that can also dramatically reduce memory bandwidth consumption. Even though Maxwell was built on 28nm, like Kepler, but Nvidia still increased the total transistor density.
An older chart made by NVIDIA: