Which do you spend more time interacting with: your operating system, or your software? It's possible to get too pedantic with the answer as ultimately everything comes back to the operating system, but really, the answer is your software. You edit a file in a text editor or word processor. You read your email in an email client. You browse the Web in a Web browser. So when it comes time to move from Windows to Linux, one of the first things you want to consider is what software you rely on in the Windows world, and what you're going to use in Linux.