Disc brakes prevent your rims from getting worn out, especially when riding in dirty, gritty, wet environment such as gravel, dirt and snow. They also provide better braking when riding in winter weather when it's icy and snowy...Other than that there aren't really any advantages. If most of your riding is done in nice weather on clean pavement you don't need disc brakes. A properly adjusted rim brakes with good quality pads stop just as well as disc brakes.