In the end the differences are minimal in performance and game specific.
But the learning curve is not. Do you really want to spend so many of your gaming hours getting a new OS to work the way you want?
Or would you rather not worry about games being occasionally 3% faster (not noticeable) and game more?
I went the wrong way, so many hours wasted learning and setting up Win8. But then I wised up and spent a little more time with my overclock. Much less time spent and much greater results.
Put your time and money in your Win7 machine.