Most of the open source drivers you'll find may produce better graphical output than the proprietary do. Sometimes you won't even notice a difference. And sometimes an open source driver works much worse than the proprietary one. I will not make a general recommendation on which to use, but here are some cases, in which certain drivers are better than others:
- If you have a nVidia card with Optimus,
you should install the open source driver from the Bumblebee Project. This is the only driver supporting Optimus on Linux. you should either install the open source driver from the Bumblebee Project, or any nVidia proprietary driver, but not the Xorg driver, as it currently doesn't support discrete graphics.
- If you want to use CUDA (nVidia's stuff for executing functions on the GPU), you should use the proprietary driver.
- If you want to use OpenCL (something like CUDA, developed by Khronos), you have to use the proprietary driver.
If none of these applies to you, it's up to you which driver you use. If you don't have any problems with the current driver, I wouldn't change it. You never know whether another one will even work at all. However, if you want to take the risk, try the drivers suggested in Software & Updates → Additional Drivers and find out which one works best.