[mortenjorck]

Affinity Designer is an excellent tool for illustration and graphic design, and it can work as a UI design tool as well (better at least than Illustrator or Photoshop), but nothing else (outside of browser-based tools) has quite leaned into the UI design niche like Sketch has.

Sketch turned an important corner when it introduced two things: Symbol overrides and scaling constraints. These two things made UI design in Sketch a massively more streamlined process than any other product, and while other packages have started to adopt them, Sketch has stayed ahead by further developing these features along with shared library support and a robust plugin API enabling further workflow-enhancing tools like Sketch Runner.

Sketch is, however, fairly terrible as a general-purpose vector editor. Its clumsy shape tools are bad enough that I usually start any icon design in Affinity Designer and then import to Sketch.