It depends, open-source driver brings better desktop experience in general, even considering only NVIDIA drivers (nouveau), since you don't need the extra performance in 90% of the cases. Things like KMS is only available in NVIDIA binary drivers in recent releases, are still kind bugged and it is more difficult to use (installing a binary driver and including the module in initramfs VS. completely plug-and-play support with open-source drivers; the work can be automated by distro maintainers, but still is not the same thing). Other things like Wayland works so slow in NVIDIA binary drivers that is simple unusable. Another example is GPU switching: for some time Linux has a very good dynamic GPU switching support using PRIMUS, however NVIDIA proprietary drivers still does not support it (maybe they can't?), so NVIDIA ends up reinventing the wheel and their implementation is really bad (Vsync issues and no dynamic switching, you either start your whole X11 session in iGPU or dGPU, so it is kinda useless).

NVIDIA binary drivers really only win in performance. Even the features in NVIDIA drivers tends to be more bugged: i.e. I use compton as my composite manager. It needs a very old OpenGL version (like 1.1 or 2.0 capability), and NVIDIA drivers still mess up and I need to activates some workarounds in compton to get usable desktop. MESA (used by open-source drivers) has a much better OpenGL implementation, and I can basically get a glitch free desktop without workarounds. I also remember getting random glitches in Chrome and Gnome Shell, just to cite more examples.

So it is not an artificial comparison. Want performance and CUDA? Yeah, go to NVIDIA. Want just a stable, modern desktop (Wayland and composite glitch-free)? Open-source drivers is the way to go.