In general, the most effective approach for anyone in any project is to apply sound PM principles in a way that makes the most sense given the situation. It is just as important for individual performers to understand and accept the needs of their managers and clients as it is for them to simplistically expect their management to just tell them what they want and stand back.
Clearly, there are some situations that call for an Agile approach like Scrum while others (large, complex, critical and regulated projects) call for a relatively "heavy" approach. Many projects can be managed with a hybrid approach. For example, an Agile software development project can be embedded into a waterfall-like product development, or process change project or program. No project in a business setting can really justify a 'seat of the pants' approach that leaves out planning and control and puts the project reins in the hands of performers who may not have the big picture in mind, or may be too immature to warrant the trust required for a truly Agile approach.
"Black and white thinking" is a terrible waste of time and talent. It leads to solutions that are sub-optimal and that invariably dissatisfy a significant number of people, often including many of the adherents of the "winning" side. On the global scale it is the thing that has caused most of history's horrific events. Let's eliminate black and white thinking and engage in dialogue that seeks to educate and inform practitioners regarding the best way to manage. Then leave it to them and their management to choose the right approach for the projects at hand.
George Pitagorsky, PMP, integrates core disciplines and applies people centric systems and process thinking to achieve sustainable optimal performance. George authored The Zen Approach to Project Management and PM BasicsTM. He teaches meditation and is on the Board of Directors of the NY Insight Meditation Center.