Density functional/molecular dynamics simulations and experimental data (x-ray and neutron diffraction, extended x-ray absorption fine structure) have been combined to determine structural and other properties of amorphous AsS2 and AgAsS2. These semiconductors represent the two small regions of the Ag-As-S ternary diagram where homogeneous glasses form, and they have quite different properties, including ionic conductivities. We find excellent agreement between the experimental results and large-scale (over 500 atoms) simulations, and we compare and contrast the structures of AsS2 and AgAsS2. The calculated electronic structures, vibrational densities of states, ionic mobilities, and cavity distributions of the amorphous materials are discussed and compared with data on crystalline phases where available. The high mobility of Ag in solid state electrolyte applications is coupled to the large cavity volume in AsS2 and local modifications of the covalent As-S network in the presence of Ag.