This is a good question, because you ask about the advantages and disadvantages of brands. The advantages are mainly twofold. First, branding allows a company to market their product with confidence. It tells the customer that they stand behind their product or service. Second, branding, if done well, can corner a market by making their service or product synonymous with excellent quality. For example, anything with the Donald Trump brand is seen as a quality product by most people.
From the point of the view of the customer, brands can be very important, because customers grow to trust brands. If a company that they trust endorses something and puts their brand on it, it can carry some weight with consumers. It is also important to keep in mind that brands connote certain lifestyles or a certain status. So, customers, who want to have that mark of status may be more apt to use that product or service.