The size of the keyboard can be determined by many factors. I will try to highlight some of the major ones you might encounter, but this is by far not a complete list of reasons. Simply put, the size of the keyboard will be determined by your needs and desires. Do you need space on your desktop? Real estate can be a hot commodity on gaming desktops. Do you have enough room for your mouse to sit comfortably next to a large slab of keys?
Bé Mun