It depends.
ChromeOS if all you do is web browsing
Windows if you generally want an operating system almost everything supports
Linux if you are a developer, okay with only most things being supported (cases where things aren't supported are like online video games or software with really crappy DRM), or want to try something new
MacOS if you got a pile of cash to burn, or are someone with an online creative profession like a video editor.
this is a huge generalization and honestly any OS can be used for nearly any purpose