Resonant Bessel-beam launchers are azimuthally in-variant structures characterized by a circular grounded dielectric slab with an isotropic metasurface on top. Previous works ana-lyzed the launchers performance for some specific cases, assuming TE or TM polarizations, inductive or capacitive metasurfaces, cavities with sub-wavelength or half-wavelength height. We show here with both theoretical and full-wave results that the inductive or capacitive nature of the metasurface has a fundamental role in the radiating behavior of these devices. Results are reported for the relevant TM-polarized case, considering air-filled, half-wavelength thick cavities. The extension of this analysis to the TE-polarized and dielectric-filled case will be discussed at the conference.