@Xsiuz_Oficial I’m still learning, but here’s my take:
Smart Materials: Uses existing materials to add textures (like dirt) that fit your model’s shape.
Designer: Used to create those base materials from scratch.
Essentially, Designer makes the ingredients, and Painter creates the recipe
@Xsiuz_Oficial You can create materials from scratch using a node-based system.
The materials you create can be used directly in Substance Painter.
Also, because it's procedural, you can easily modify or add new elements later without restarting.