Explain StatelessWidget vs StatefulWidget and when to choose each

This tests your understanding of immutable configuration versus mutable state. StatelessWidget is immutable and rebuilds only when its parent passes new arguments. StatefulWidget splits the disposable widget from a persistent State object that survives rebuilds. Choose StatelessWidget for static content like icons or text, and StatefulWidget for interactive elements that respond to input or animations. A red flag is claiming StatefulWidget is more powerful and using it as the default for every screen, adding unnecessary lifecycle overhead.