While digitizing is a time-consuming process, it has some advantages over scanned raster images, particularly if you want to use the map for geographic analysis.
Digitizing a map creates a vector image that is just like any other MapInfo map layer. Each feature you digitize becomes a map object that you can edit, move, customize, or attach data to. You can include as much detail as you want to trace from the paper map.
A raster map, on the other hand, is simply a graphic image that is used for display purposes only. You cannot edit or attach data to it. It is used as a backdrop for other map layers. Its main advantage over digitizing is input speed.
For more on raster images, see Registering Raster Images.