One must always be careful to differentiate in regards to the hardware because there is no one “driver”; its plural. I’ll copy part of what I wrote elsewhere recently and then expand it just a bit in regards to being relevant to this thread:
Here is a very brief (and grossly simplified) description of (the key components of) that for contemporary AMD graphics adapters under the X Display Server:
[ul]
[li] kernel component[/li][LIST]
[li]DRM/KMS kernel driver … the radeon driver (radeon.ko) … what you see listed if you use “lsmod”, “lspci”, etc… [/li][/ul]
[li] userspace components[/li][ul]
[li]DDX driver … the Xorg driver (radeon_drv.so) [/li][li]3D/OpenGL (Mesa) driver) … for which there exists, applicable to the particular hardware, the r300g (r300_dri.so), r600g (r600_dri.so), radeonsi (radeonsi_dri.so) [/li][/ul]
[/LIST]
As for the 3D drivers, their naming represents a class of hardware that the driver begins coverage for (Example: r600g begins for r600 adapters up through to NI (Northern Islands)). The g appended on the names of the two listed above denotes that they are a gallium type of Mesa driver (distinguishing it from classic Mesa drivers … there used to be (actually, originally were only) classic r300 & r600 drivers, but these have since been removed when the gallium versions became mature). Support for SI (Southern Islands) class hardware (and now extended above for the future CIK/Sea Islands adapters) was developed using a gallium driver from the very beginning, so no such naming distinction is used (needed). The support for SI devices (i.e. radeonsi driver) is slowly coming along, but is still not as mature or feature-full as the r600g.
So, for hardware that falls within the coverage of the r600g in the OSS world (which is essentially HD2000 through HD76xx, and all the APU parts (they may have HD8xxx gpu names but they are indeed rebrands, and not of the GCN arch)), the difference between the OSS stack and the prop. stack is, in the general case, not particularly meaningful (IMO) to warrant use of the prop. driver any more. The one exception of where the prop. drivers will provide a much better experience is with OpenCL. Other then that, PM is now on par, accelerated video decode tips in OSS favour, 2D is much better with OSS, 3D is slightly better with prop. There, of course, will be corner cases which will go one way or the other, and perhaps in some cases in a much more meaningful way then that of the general case. In addition, and this is the real important point, you’d have to profile your particular application usage and see if it makes sense for you. I can only advocate what I think makes sense on general terms. And given the OP is using a HD64xx adapter (a very weak GPU series), I’m pretty sure that there are no pressing 3D or OpenCL needs to be met, so I would indeed endorse the recommendation to, after upgrading their kernel and graphics stacks, switch to the OSS drivers (note: they will still have to manually set a few options to take full advantage of the new features and capabilities)
For hardware that falls within the scope of coverage of the radeonsi in the OSS world (i.e. HD77xx through current and future parts, less the current APU parts as explained above), if you’re in anyway using 3D above basic desktop, then you would currently be much better served via the prop. drivers.