The essence of Agile movement, whether in new product development, new service offerings, software applications, or project management, rests on two foundational goals: delivering valuable products to customers and creating working environments in which people look forward to coming to work each day.
If your goal is to deliver a product that meets a known and unchanging specification, then try a repeatable process. However, if your goal is to deliver a valuable product to a customer within some targeted boundaries, when change and deadlines are significant factors, then reliable Agile processes work better.