I have a rather basic question. What is the benefit of using covariates in CBC/HB instead of estimating the utilities for each subpopulation individually? Illustrative example: Imagine I want to use gender as covariate and I have a sample size in each gender split that would allow to do the estimation for males and females separately. What is the difference between using covariates and doing the analysis for the subgroups?

From my experience differences between groups are higher if you estimate the utilities for each subpopulation separately compared to using covariates. Is this higher difference "Noise" which is corrected for when using covariates?

Many Thanks

Rainer