Typically, if a real estate agent is asked to judge the value of a piece of property, he would do so based on information of recent sales or purchases of similar properties in that area.
Though this may give a fair idea of the property’s market value, an official property valuation would carry more weight. E.g. if you need to use this piece of property as a security against a loan, the bank’s loan approval process would be faster and smoother if the property is certified by an official evaluator. Many banks now insist on valuation certificates before issuing loans using properties as security. The value thus certified may also have chances of getting a higher amount of loan sanctioned.
Another benefit of official valuation is that it is a useful negotiating tool when selling the property.
Such certification also becomes essential in situations where the correct value of the property has a legal bearing—such as, a will statement, insurance papers, business balance sheets etc.