If I understand you correctly, the DEM contains the values (elevation) that you want to use to create your cross sectional visualizations to show faults or fractures in the terrain. You may want to look into getting your hands on some LiDAR point clouds of the area, which can be used to extract the bare earth only and create a digital terrain model (DTM, excluding above-ground structures).
The hillshade layer doesn't show elevation, but rather uses the elevation data from the DEM and an assumed position of the sun to infer which areas will be shaded under some given circumstances. Unless you are concerned with the illumination of your fault lines by the sun, it is unlikely this will be useful to you.