Actually, compared to other OSses, windows slows apparent execution of the computer it's installed on.....drastically.
Then again, not many of the games that people are wild about are ported to non-ms OSses, so there you go; however, it remains that windows slows a machine down horribly.
The recommendation that favors win10 over win7 is merely because people are in the consumer cattle chute and it behooves everyone if you move to the newest release, and cut their work and costs of supporting older OSses with drivers down; and newer OS releases are focused more on the newer hardware platforms, and the hardware sales folks LOVE that.
It's a symbiotic relationship between software producers, and hardware manufacturers; and its goal is to regularly separate you from your money, chasing after the latest and shiniest trinkets offered for sale.