The dependence of the effective anisotropy and of the magnetization reversal processes on the deposition temperature of a series of epitaxial Fe/MgO/GaAs films, grown by a combination of laser ablation and sputtering, has been discussed and correlated to their local morphology and crystallinity. The transverse susceptibility measurements have evidenced the presence of a fourfold effective anisotropy for all films, irrespective of their deposition temperature and local morphology, with a constant value very close to that of single-crystalline iron. The magnetization processes evolve with increasing deposition temperature from a nucleation-expansion-propagation mechanism, taking place in smooth continuous films, to pinning, occurring in self-patterned films with homogeneous distributions of defects, and then to fully isotropic reversal, for tiled films composed of rectangular elements.