During my fifty plus years in architecture, I have learned the benefits of working with a single team of people who, together, are better than the sum of their parts. When the design team (architect and engineering) and the build team (contractor and sub-contractors) come together under one project contract, the method of project management and delivery is called Design-Build. A cohesive effort on the part of such a team benefits the customer in a number of ways, not the least of which is having a single entity and one contract to manage. The results of this method of delivery are illustrated in the accompanying visuals.
(Graphs courtesy of Design-Build Institute of America)