The goal of this study is to establish the rain properties and sub-cloud environments in which we can expect the largest benefits of a predicted over a parameterized shape parameter – or otherwise, in which clouds the cheaper approach may be sufficient. These regimes will depend on the dominance of different microphysical processes in the sub-cloud layer: It is known that a three-moment approach with predicted shape parameter would impact gravitational size sorting. In heavy precipitation, the interplay between rain self-collection and rain breakup is known to be crucial in shaping the size distribution. In a dry sub-cloud layer, evaporation is expected to contribute to a broad size distribution. A rain shaft model is applied to consider a wide range of atmospherically relevant rain scenarios. The investigation includes a varying cloud base height, rain intensity, as well as sub-cloud relative humidity. A systematic comparison is performed among the original two-moment scheme, the three-moment development, and a spectral bin microphysics scheme which serves as a reference. Results are interpreted in terms of the prevalent microphysical processes.