3D accelerated support is poor for several NVIDIA GeForce series as that's being held up until NVIDIA publishes the necessary signed firmware files for these newer GPUs.
The NvBoost support that's mainline with Linux 4.10 and beyond was of big help to the higher-end Kepler cards for squeezing out more performance. Again, it's not enabled by default but you need to boot the system with nouveau.config=NvBoost=2. Likewise, the re-clocking code in Nouveau isn't yet dynamic but you must manually re-clock your supported hardware for better performrsance.
So for now the bottom line is that Nvidia Drivers has far better 3D acceleration and better overall performance over the Noveau drivers