I would recommend Windows 10 (Pro) as the operating system delivers higher FPS in games because it is the only operating system that has DX12 whereas Windows 7 only has DX11. And overall Windows 10 is a nice OS and suits gaming very well. The only downside is, some updates of Windows 10 can cause blue screens if you do certain tasks like gaming or anything that puts the operating system on load. However Microsoft are working on them and fixing them.