Erbium-activated silica-titania and silica-hafnia planar waveguides have been prepared by the sol-gel route. The films were deposited on vitreous silica substrates using a dip-coating technique. The parameters of preparation have been chosen to optimize the waveguides for operation in the near-infrared (NIR) region and to increase the luminescence efficiency of the metastable 4I13/2 state of erbium ions. The waveguides’ properties were determined by m-line spectroscopy and loss measurements. Waveguide Raman and luminescence spectroscopy were used to obtain information about the structure of the prepared films and about the dynamical process related to the emission in the C telecom band (1530–1565 nm) of the erbium ions. The results are discussed with the aim of comparing the structural and optical properties of erbium-activated silica-titania and silica-hafnia planar waveguides.