Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) is a popular control scheme, for the stabilization of underactuated mechanical systems, formulated in Port-Controlled Hamiltonian (PCH) structure. However, robustness enhancement of this control approach towards external disturbances remains an challenging and an open problem. In this paper, an experimental comparative study between two different IDAPBC approaches is proposed. The first controller is a nonlinear Proportional Integral IDA-PBC, while the second one is a model reference adaptive IDA-PBC. To evaluate the effectiveness of both controllers, various real-time experimental scenarios have been conducted for the stabilization of the inertia wheel inverted pendulum. For the sake of a fair comparison, different performance-evaluation criteria have been proposed to quantify the control performance in terms of convergence and energy consumption. The results show a better performance of the nonlinear Proportional Integral IDA-PBC controller compared to the model reference adaptive IDA-PBC controller.