Regardless, the 950 will have support for Directx 12, use less power, and be a little faster.
According to my benchmarks my 960 is about 45 - 50% faster than my friends 670.
We both played the same game on similar computers at the same settings.***
I average about 15 - 30 more FPS than he does.
***
The Secret World - Max Settings
Xeon W3520 (i7-920) - 6 GBs of RAM (me)
vs
AMD Phenom II X6 1045T - 8 GBs of RAM(him)
GTX 960 - 1080p / 85 - 91 fps
GTX 670 - 1080p / 65 - 78 fps