How important is multi-band (dual-frequency) GPS?

Specialist communities and expert testers consistently say multi-band matters in tree cover and dense urban environments and is largely irrelevant on open roads and tracks. The Forerunner 255, 965, and Coros Pace 4 support it; the Forerunner 55 and 165 and most budget watches do not. If you run trails or downtown in a major city, reviewers recommend prioritizing it.