Ratios of 1σ marginalised uncertainties relative to 1σ marginalised uncertainty for D_g. We assume a wCDM model and marginalise on 20 galaxy bias parameters (one for each redshift bin). Orange lines show the ratio for D_z and green lines show the ratio for D_g,  z. Solid lines are for a DESI-like survey, while dashed lines are for an Euclid-like survey. We see that D_z improves constraints by up to 50% compared to D_g, and the combined analysis D_g,  z improves constraints by up to 80%.