Two different molecular dynamics-based models are compared with respect to their ability to predict the number and the distribution of trapping sites of a molecule in a rare-gas matrix. The two approaches are applied to the same problem: anthracene molecules trapped in an argon matrix. Both methods give a small number of trapping sites with similar structures, but the distributions of sites in each model are different. In all stable sites, the molecule was found to lie on either the {001} or the {111} plane of the crystalline argon. We propose a structure for the most stable site in which anthracene lies in the 6 substitutional site in the {001} plane.