The main difference is ownership of the flow.
By outsourcing CAD to BCI, the CAD solution developed by BCI can be partially or completely owned by you.
Complete ownership means you can request BCI to develop the solution from scratch or start with your existing flow/solutions.  You will completely own the result. Partial ownership means using a pre-implemented flow from BCI and customizing it to fit your needs.  The customization part can be owned by you, while the based pre-implemented flow will continue to be owned by BCI.
By using BCI as CAD services,  you are choosing not to own the flow and, as a result, reduce the cost and effort required by owning the flow (see the total cost of flow ownership below).  But what you gain is the capabilities that come with Dagogo.