My experience (my own and as a tech worker) is this: Casual users go online, browse, email, use FaceBook and use hardly any drive space other than the operating system and a small number of programs they download. Their hard drive is more empty than full. Some are hoarders; they download programs and keep them even if they never use them, they download fonts, pictures, music, video and keep every file they ever create. Their hard drives fill up rapidly. Some keep large collections of music, and/or video and photos. They use up a large amount of drive space; some run out quickly while others move files on and off the computer to stay within the confines of their drive. What kind of user are you, where will you keep the bulk of your stuff, and on which platform? Plan carefully because if you guess wrong you could spend a weekend rebuilding everything.