One difference between the FV3 and the GFS is in the smoothness of precipitation. The FV3 has a much smoother depiction of accumulated precipitation. The following comparison image uses the same grid resolution (0.25 degree) for both the GFS and FV3, so that is not to blame. Fanglin Yang, one of the leaders of the FV3 development at EMC, hypothesized a diffusion setting in the FV3 may be the cause of the differences, but not much investigation has been done to this point.