When would you use Angular signals instead of RxJS Observables?

I pay attention to hot versus cold streams, subscription side effects, completion, and whether multiple consumers should share work before converting. Errors from an Observable converted with toSignal surface when the signal is read, so the UI still needs an intentional error model. For command flows, I keep request identity and stale-response prevention visible rather than relying on last-write timing. The architecture is clearer when domain state has one owner and interop is localized instead of alternating repeatedly between signals and streams.