Fitted bedroom furniture has many advantages over shop bought furniture. It is especially useful if you have a smaller room or a room with awkward spaces / sloped ceilings. Fitted bedroom furniture is made to the exact measurements if the room meaning that no space is wasted. You may find that you can fit allow more into your bedroom than you first thought.
Sliding wardrobe doors take up less space as they do not open outwards but instead slide behind each other. You can configure the inside of the wardrobe to ensure it has all the space that you require such as hanging space, a shoe rack or shelving.
Most fitted furniture companies will be able to create you a 3d visual of how the room should look when it is finished. This will allow you to move things around and finalise on the design that you are happy with prior to the ordering being sent to the factory to be made.
The only downside with built in furniture is that you cannot usually move the bedroom furniture around as it will have been built to fit along that specific wall.