Comment Regular on Phoronix (Score 1) 185
Doing opensoure vs closedsource comparison has also being been done on a regular basis at phoronix.
To sum things up:
Current Mesa/Gallium3D stack is opengl 3.x only, proprietary drivers are 4.x (but work is being done, including by paid developers)
AMD:
except for the latest generation (where the opensource driver team is still debugging the support - but at least AMD does publish documentation and pays a few opensource developpers on their own, so I WILL EVENTUALLY end up supported), the opensource drivers have a decent performance, which has progressively went closer to the proprietary. For slightly older cards you might as well use the opensource drivers (a bit less buggy). For really old cards, even AMD is acknowledging it: they dropped the support from catalyst and are pointing toward the opensource drivers as the preferred drivers.
In short: if it's not the latest generation of hardware, give the opensource drivers a try. Unless you want to only play OpenGL 4.x games on your machine.
Nvidia:
Here, take this pair of dice, they are better performance predictors...
More seriously: performance is rather random, mainly due to the fact that the opensource drivers are entirely developed by reverse-engineering on whatever the developers hapenned to have (if you happen to have a slighly different model, there isn't much they can do). So random bugs and problems even in the middle of an otherwise supported range.
For newer cards the situation is even worse performance-wise, because they boot underclocked by default, and the driver don't know how to ramp-up clocks as demand increases.
At least, opensource drivers follow linux standards and some features aren't utterly broken.
So for know, stick to closed-source drivers - best performance ever -, unless you happen to need a feature which works differently under windows (and thus wasn't ported to linux). In that case, you might do an attempt with opensource and se on which random result you end-up.
With time, this is bound to change: Nvidia might get interested in helping a bit (they hey released a few bits of useful information regarding the Tegra line of embed GPUs).
Intel:
Has a bit lower support than their (windows proprietary) driver (opensource Linux is GL 3.x, Windows is GL 4.x), and their opensource drivers are a bit slower.