If you looking to build a mining only rig, linux is the way to go if you have the time and courage to work with it(I'm assuming you don't have a lot of experiences with linux) The benefits of using linux is the system is less resource intensive on your rig, which means higher hashrate YEAH. The advantage of using Windows is ease of use, but I would advice you to stay away from Minergate because you are not utilizing your GPU's to its potential. Minergate is super easy to setup and start mining but the alternatives on Windows as well as Linux, will yield you better results.
Happy mining!