For gaming at 1080P , you are looking at about 10 more FPS from the R9 380 which is ok but you wont see a difference if you get lets say 90 FPS. At higher resolution, the R9 380 just runs past the GTX 960.
http://www.tweaktown.com/articles/7568/dx12-benchmarked-ashes-singularity-amd-nvidia-gpus/index.html
Only one game but it looks like DX 12 brings out the best in the Radeon architecture .
Having said that if I could wait a few months to buy then I'd wait to see ho much better AMD's Polaris and nVidias new cards will be