Which redshifts will gravitational waves best reveal dark energy?

Using simulated gravitational wave catalogs from LISA and the Einstein Telescope, this analysis finds that raw distance measurements alone can't decisively separate six competing cosmological models — but derivative-based diagnostics identify narrow redshift sweet spots (around z≈1.6–1.8 for ET, z≈2.6–2.9 for LISA) where discrimination power peaks. The finding tells future observing campaigns exactly where to concentrate effort, rather than treating all redshifts equally.