Well, for one, both the Designer and Builder both know what the other intends to do. The designer in this case is not someone who, once paid, wishes you good luck.
We are that designer who is with you all the way; we work to achieve what has been the creative product of the client and designer. Also, the designer in this case, as a builder has 30+ years building experience and knows what works best in the field.
Thousands of dollars (some times more than the design cost itself) can be saved by using 'ease of construction' methods and simple detailing for framers. In many cases the RCI designer is the Project Manager for that job. It doesn't get better than that.