Both Substance Designer and Photoshop can create textures for 3D but they approach the task from fundamentally different directions.
Substance Designer
Creates textures through node-based procedural graphs. Output is resolution-independent and infinitely tileable by design. Changes propagate through the entire graph so iteration is fast and non-destructive.
Photoshop
Works with pixel data directly. This approach is intuitive for artists from traditional backgrounds and excels with photographic source material. However results are resolution-dependent and seamless tiles require manual work.
When to Use Each
Use Substance Designer for procedural tileable materials like brick walls concrete and fabric. Use Photoshop for one-off textures hero props or when your source is photographic reference. Many studios use both.