Radeon Linux OpenGL Driver Continues Giving Its Best Against Windows 10
First up are some of the open-source OpenGL games where it wasn't a "port" to either platform.
Since last year AMDGPU+RadeonSI has largely become faster than Radeon Software's OpenGL driver, which is also shared with the AMDGPU-PRO code-base. In the case of OpenArena it's one of the gaming tests where the open-source Linux driver stack is significantly faster than Windows.
With Xonotic it's an interesting case where the RX 580 is performing about the same between Windows and Linux but the RX Vega 64 does perform much better on Linux. But as you may see from the results, the performance between the RX 580 and RX Vega 64 with this particular game is about the same on Windows: this is either due to the overhead of the Radeon Software OpenGL driver or some lack of Vega optimization in place as I don't imagine AMD is caring much about the performance of the Xonotic open-source game compared to all the AAA game titles on Windows.