Registered documents are admissible in the court of law since they have evidential value in the eyes of the law. This means that un-registered documents are not readily acceptable and admissible in a court of law.
Registered documents safeguard the interest of a buyer since they take effect against every un-registered documents relating to the same property. In other words, the registration of documents preserves the title of the buyer.
Registering your document puts it on the government record which renders credibility to the document and makes it a notice to the public at large in respect to the subject matter of the document.