ROG Xbox Ally runs better on Linux than the Windows it ships with — new test shows up to 32% higher FPS, with more stable framerates and quicker sleep resume times
www.tomshardware.com
Jury's still out on Microsoft's optimization.

Edit: The video of that’s the original source of the test results had flawed testing for some of the games and seemingly didn’t set the same tdp limits when switching between the OSs. I’m guessing we’ll see other people test this out later, but for the time being it’s best to assume these results are exaggerated or wrong.