The performance of optical devices relying in vanadium dioxide (VO_2) technology compatible with the silicon platform depends on the polarization of light and VO_2 properties. In this work, optical switching in hybrid VO_2/Si waveguides thermally triggered by lateral microheaters is achieved with insertion losses below 1 dB and extinction ratios above 20 dB in a broad bandwidth larger than 30 nm. The optical switching response has been optimized for TE and TM polarizations by using a homogeneous and a granular VO_2 layer, respectively, with a small impact on the electrical power consumption. The stability and reversibility between switching states showing the possibility of bistable performance is also demonstrated.