If you had to choose one UML diagram for architecture — which one?

If you choose a UML diagram to describe the system architecture, the most commonly selected is the Component Diagram.

It shows the main modules or components of the system and their interactions, which helps to understand the structure and boundaries of subsystems. This is convenient for high-level architectural representation, especially in distributed systems.

Alternatively, for displaying data flows and interactions, a Deployment Diagram or a Class Diagram can be used, but the Component Diagram is the most versatile for architectural overview.