On 4K a Windows machine looks tolerable, but I'd hold back from calling it "great". It's more like the deficiencies are less obvious.
Windows has long been indifferent to faithfully representing fonts, to accurately representing colors. They've always promoted readability at the cost of mangling fonts, and of performance.
The macOS rendering system has always been set up with high-DPI displays in mind, they were able to work out a lot of rendering problems on things like the iPhone and iPad before committing to the computer version of same.
Windows on a 4K display looks close to but not quite as good as a Mac on a 1440p display, it's just that stark.
This is all personal preference obviously, but having done a lot of design work I'm more easily irritated by little quirks.
