Designer's main strength is that it approaches texturing in a procedural way with the use of a node graph workflow. You can create full materials composed of multiple textures without the need for additional images.

You can create textures at any resolution without quality loss, create and use nodes of your own or made by others, and it can adapt to any pipeline.

Substance designer allows users to create custom substance files, it offers a lot of power with a mix of workflow of working with procedural textures and bitmaps.

It has the ability to export sbsar files, these can be put into most game engines such as Unity and Unreal Engine 4 allowing in engine tweaking of procedural content.