Photonic modes in 1-D and 2-D silicon-on-insulator photonic crystal waveguides periodic or containing line-defects, are fully explored by means of angle- and polarization-resolved micro-reflectance measurements. Both quasi-guided and truly guided photonic modes are probed with a frequency-wave vector range that is greatly expanded under attenuated total reflectance configuration. It is shown that the presence of a supercell repetition in the direction perpendicular to a line defect leads to the simultaneous excitation of defect and bulk modes folded in a reduced Brillouin zone. Consequently, the group-velocity dispersion of the defect modes corresponding to different polarizations of light can be fully determined. We show also that the measured dispersion is in good agreement with full 3D calculations based on expansion in the waveguide modes.