I recently ran a few tests with a GTX 780 vs. a GTX 970. I rendered two different scenes with each of them. The GTX 780 rendered scene A in 50 seconds, scene B in 225 seconds. The GTX 970 rendered scene A in 59 seconds and scene B in 230 seconds. So the GTX 970 is 5 to 10 seconds slower than the GTX ...