Torsion- and bending-dominant modes of a zigzag-shaped piezoelectric vibrational energy harvester were compared in terms of power generation using experimental and numerical methods. Output power measurements from 25 discrete mass loading configurations led to three major observations: (1) a torsion-dominant mode can produce a higher level of power compared to a bending-dominant mode, (2) generated power in the torsion-dominant mode displays a V-shape curve under certain mass loading, rather than continually increasing as a function of mass, and (3) generated power in the bending-dominant mode is largely independent of mass. These observations differ from the conventional wisdom that bending modes are better for energy harvesting and that power increases as a function of added mass. Numerical analysis is used to validate the variation of generated power and is found to be in agreement with the experimental results. Analysis of the displacement and gradation angle of equi-displacement measurements of the beam are used to provide understanding of the influence of dynamics of the energy harvester on power generation.