Both of these drivers are built for Linux and work fine for most Nvidia graphics cards with no issues. But it’s known in the Linux circles that for a while Nouveau drivers just wasn’t up to par, when it came to the heavy graphic rendering intensive work needed in games and 3d animation, when compared against Nvidia.
But latley with new developments in the Nouveau driver project it seems the gap has been closing.
Linux4UnMe a show with a channel on YouTube, recently compared the two drivers in a nice demonstration of Urban Terror. See below video.