Hi Mihhail,
In terms of using a DSM instead of a DEM, it depends on your specific analysis and the data you have available. For example, DSMs include the height of all features on the ground surface, such as buildings and trees, while DEMs represent the bare earth surface. If you are interested in measuring the ruggedness of the bare earth surface, then you should use a DEM. However, a DSM may be more appropriate if you want to include all features on the ground surface in your analysis. Remember that DSMs may produce values higher than DEMs since they include the height of objects on the ground.
In any case, it is essential to understand the data's characteristics and limitations, such as its spatial resolution, accuracy, and vertical datum, before using it for any analysis or modelling.
Thanks,
Omar