This days Ars technica wrote a Steam OS benchmark, not even a Steam Machine one, with old hardware (Nvidia GTX 660) that is Kepler and not the modern Maxwell (750 Ti and 9xx series) Steam Machines will have, also a Pentium G3220 when i3 will be the minimum at the Steam Machines.
Other rare thing is not to test (or publish) at 1080p (almost 2k) and 720p (almost 1k) that are the TV resolutions and do it at the higher and rare 1792x1120 that we will not find at our TV sets.
With this rare one rig benchmark, and two non opengl games tests, that are ported from MS WOS to GNU/Linux this cheap way knowing they will perform less they found the conclusion it is worse, and others repeat it as if it where true for every case.
It would be even a better benchmark one made with an Nvidia based Apple machine, including OSX too.
Ars technica writer mentioned http://www.phoronix.com/scan.php?page=article&item=win10-nv-ubu1504&num=5 but not other bad copier of this went there to read about a good benchmark that still is good news for MS WOS 10 desktop computers vs the use of Steam OS in dual boot if what you want is speed or play at ultra settings, as a hard gamer (and not a console player) would like to do.
But MS WOS 10 has other issues, as viruses (that slows gaming) defragmentation, and more or less a re installation every year because each day it gets slower, and that is why MS WOS 10 + Steam, that is already a product, the alien alpha, is not a successful one, and Steam Machines will be, so much that to speak bad about them they have to make unfair tricks.
Not to say that 1.600 games are more game titles that any other console had at the end of their cycle, and Steam Machines have it at their beginning, titles are cheaper than at any other console, the Steam Controller is a piece of art, made with a lot of user feedback, it has 70% of the most played PC games and as the future is Vulkan based games performances will be similar at every OS.
And he was right, he already spent money on a expensive computer rig, and even for TV playing the Steam controller plus the Steam Link are a better purchase.
But he is not the target, the target is all those console gamer that do not want to buy a expensive desktop computer to play those amazing PC games, and like to play with TV sets instead of doing it with desktop monitors.