I experimented with both windows 7 and windows 10 both fully updating both and turning off updates on both as well. And i can safely say that playing fsx on a fresh install of win7 with no updates(iso u can find on other websites) is way faster than windows 10. Im in the process of getting screenshots of fsx on both so you guys can see this is facts 

Erm.... I found the exact opposite.. We all have very different hardware, & thus will ALL have different results. 

Remember, older hardware will, obviously, not be optimised for an up to date operating system.

I prefer my OS to be updated. far more secure that way.