Just throwing this out there as a reminder, Microsoft is ending the extended support for Windows 7 in 2 years (Jan 14 2020). So you'll eventually have to make the switch. For now I'd save the money and stick with Windows 7.
I use Windows 7, works great. Personally I find it better then Windows 10 simply because it has less junk I don't want built in. And I'm not sure if it's still an issue, but Windows 10 used to force updates that had a tendency to break stuff.
You should search on youtube some 10 vs 7, there are a lot of good reviews with pros and cons. I use win 10 and i never had any troubles with it. Sure it has that force update but i had no problems so far and i use it for 2 years already.
All the software you need for game development will run on it, there's no problem there as the OS has been around for years now. However, now that a lot of companies push for subscriptions models you will run into conflicts if you decide to accept such updates too frequently (turning yourself into a beta tester, pretty…