Are chest straps really more accurate than wrist-based heart rate?

Yes, by a clear margin in the reviews we read. Specialist communities like r/Garmin and r/Polarfitness repeatedly note that optical wrist sensors suffer from cadence lock during running and lag during interval work, while ECG-based chest straps respond instantly. dcrainmaker.com and other expert testers routinely use chest straps as the reference truth when validating wrist devices.