Official Ubuntu Community’s mundane reasons in favor of Linux:

Windows programs generally recognize two types of problems: those that they were specifically designed to handle (which they make unbeatably easy), and everything else (which they make unbearably difficult). Most Windows users find everything very intuitive except “that incomprehensible geeky stuff”, which usually means the contents of the Windows folder, the registry, or DLLs.
Linux users often find themselves learning bits here and there, but rarely hit a wall of incomprehensible geekiness. This can be harder at first (where Windows wouldn’t make you learn), but it pays off in the long-run (where Windows wouldn’t teach you the skills).
For example, Windows encourages you to discount its text-based interface (cmd.exe) as incomprehensible geeky stuff, whereas Linux encourages you to learn its text-based interface (the terminal) one step at a time. You start by copying and pasting terminal commands, then as the months go by, you start to understand what different commands do. People that keep learning can eventually build whole programs out of terminal commands. (source SwitchingToUbuntu/FromWindows/Philosophy – Community Ubuntu Documentation.)

However my reasons for using Linux instead of Windows are practical. Click to follow those reasons.