I'm not sure what mechanism Windows would have to close all of your Firefox tabs and replace them with something else. I own two Windows 10 machines, and have never seen (nor heard of) anything like that. I use neither IE nor Edge, but use Chrome and Firefox constantly throughout the day.
In my experience, Windows' biggest issue is the Windows Update service seems to be fragile. I have to use the troubleshooter to repair it every so often. But, I've used OS X from 10.3 through 10.8 and a few flavors of Linux, and both presented more drawbacks than advantages for our family, compared with Windows, so we (mostly happily) still use Windows.
(Frankly, I'd like to move the whole lot over to Chromebooks or Chromeboxes, myself.)