That was such a rude answer by James Mason. Who said he can't play games with those specs. Obviously he can't play the latest titles but he can still have fun with some last gen games released 2-3 years ago like Counter Strike Global Offensive, Far Cry 3, Crysis 2, GTA IV, Battlefield 3 etc.
Well SLGaming, you could go with either one of them as both the Operating Systems perform mostly similar as far as Gaming goes. However, my personal choice would be to go with Windows 10 as it presents you with some new features and security updates. Though it's all up to you, both 7 and 10 are great OSs.