Best OS for gaming?

Solution
Windows 8.1 gives 10FPS boost to some games though and 100MB lesser RAM usage.
And both of them has the same price:
Windows 7 Professional 64-bit: $139.99
Windows 8.1 Professional 64-bit: $139.99

And Windows 8.1 has a messy lay-out though, watch out for that if you're pretty primitive with the OS.
Or you could have the choice to explore. Like what I did. But it was a pain. lol
I can vouch for Windows 7. It is a solid enough OS that it has been widely accepted in the gaming and business world both. Very stable platform on which to game.

That being said, I will be upgrading to Windows 10 if it turns out to be the OS the preview is revealing. MS seems to have taken customer suggestions to heart after the debacle that was Windows 8 and applied many of the features people want in addition to bringing back the beloved desktop.
 
Windows 8.1 gives 10FPS boost to some games though and 100MB lesser RAM usage.
And both of them has the same price:
Windows 7 Professional 64-bit: $139.99
Windows 8.1 Professional 64-bit: $139.99

And Windows 8.1 has a messy lay-out though, watch out for that if you're pretty primitive with the OS.
Or you could have the choice to explore. Like what I did. But it was a pain. lol
 
Solution
They are both good oses in my opinion as I have used both. I would wait though for people to test out win 10 as it may boost games as it support direct x 12. This may affect frame rate dramatically and it should have a huge improvement on the memory management.
 
I suggest sticking to Windows 8.1

DX11 is natively supported and games that are made for DX11 (i.e Battlefield 4) will benefit from this. It'll have performance boosts too.

Also, there are rumors that if you've got Windows 8/8.1, you'll get the free update for Windows 10. (But that's just a rumor, it's bound to change at some point.)

Windows 8.1 will boot you automatically on Desktop rather than booting you on the Metro like the regular Windows 8 did.