Tests were performed by G. Gray and J. Daniels at NOAA/NESDIS/ORA/ARAD/FPDT that showed statistically improved GOES retrievals were made using the AVN model, versus the Eta model. It appears that the temperature forecast from the AVN model is slightly better (the moisture forecast, slightly poorer) than that from the Eta model. Thus, as the physical GOES retrieval algorithm allows much larger changes [also read as "improvements"] to the moisture profile (versus the temperature profile), the better first-guess temperature data (i.e. from the AVN) are preferred. Operational GOES retrieval processing at NOAA/NESDIS/OSDPD/SSD also uses the AVN model as the first-guess.
[N.B. The AVN model is currently undergoing a name change to the GFS (Global Forecast System).]