There Is No Single Best Organizational Structure for Managing Projects …
There are a few classical organizational models, with variations on each; and each has both advantages and disadvantages with respect to how effectively an organization can manage and deliver multiple projects.

Organizational structures are a compromise between several factors: the need for administrative and financial control, the need for technical direction, the need to maintain ongoing operations while satisfying project customers, product development stay ahead of competition, responding to market and technology changes, and basic human needs for direction and attachment.

No single organizational structure is ideal for the project management methodology. Organizations change as they grow and diversify. They are different at different stages of development.