RADV Mesa 17.1-dev vs. AMDGPU-PRO 16.60 Performance
When running Dota 2 at just 800 x 600 with OpenGL, Mesa 17.1-dev is significantly faster than AMDGPU-PRO's binary OpenGL driver. The open-source GL driver was faster by 40%.
But when switching over to the Vulkan driver, we see AMDGPU-PRO's performance pick up in going from 75 to 107 FPS. Meanwhile, RADV's performance was lower than RadeonSI OpenGL at 106 vs. 98 FPS. Thus at least for this low CPU-bound resolution, AMDGPU-PRO 16.60 was faster with Vulkan but it was still rather a close race especially considering the limited effort and unofficial support of RADV.
Moving up to 1280 x 1024, it was a similar story of RadeonSI beating out AMDGPU-PRO's OpenGL performance by a lot while the Vulkan performance had leaned in favor of AMDGPU-PRO on this Radeon RX 480.
As the resolution increased, the Vulkan lead in favor of AMDGPU-PRO compared to Mesa 17.1-dev had increased.