We report a study of the physical properties of free-standing HVPE-GaN quasi-substrates. A variety of characterization techniques was employed in order to characterise in a comparative way the two sides of the films. The as-grown Ga-face was found to have lower density of both, structural and impurity defects. This leads to a lower concentration of free carriers and residual strain in the Ga-face compared to that in the N-face. The optical properties were found to be strongly influenced by the specific defect structure in both faces.