Windows 10 will have a bunch of shit you're already used to in 7, with 8.1's significantly increased performance tech. Since the learning curve will be very small going from 7 to 10, I'd go with 10 to get the most from your machine.
I'll probably just VM a development test copy of Windows 10 over the next few weeks to see what it's like. I'll probably upgrade eventually, though no game is using DX12 right now.
windows ten by a mile. Been using it on several computers now for a while, and updated my phone to windows 10 also. Microsoft is on their game, everything is very well made and runs very smoothly.