Designer enables you to do the following:
Carry projects with you, work offline, and save projects to disk.
Keep a project open for an extended period of time.
Work on multiple projects at the same time.
Experience higher performance while designing and developing a model. Processing is performed on the local CPU.
Enjoy a smoother interface with fewer clicks and fewer sub-windows to resize or close.
Benefit from an included development/debugging environment and integration with other client-based tools for editing and debugging.
For a list of features, and details about them, see Section A.0, Designer: An Effective Tool.