On a more practical level most home owners want to control light, dark and other features while extending the living space. Additionally, a homeowner may use sliding closet doors with mirrors to make the inside a room appear larger or create perceptions to control the ambiance of the space.
When you are looking at the front door designs keep in mind the rest of your house. If you have a specific style throughout the house you should try to have the front door design match. It would detract from the style that you have already worked so hard to create in your home if you choose a door that clashes with this style.
The horizontal doors used on closet sliding doors move along a track mounted overhead and a floor guide for stability. To manage the smooth movement they‘ll have cushions and buffers on the ends to prevent damaging adjacent construction to ensure a smooth gliding motion when operated. Closet sliding doors of the vertical variety are seated in a groove, much like dresser drawers to ensure they glide in one direction.