The objective of this paper is to compare the robustness performance of continuous time periodic controller with conventional non-linear sliding mode controller (SMC) for a highly non-linear system cart-inverted pendulum. The goal is to determine which control strategy delivers better performance to pendulum's angle and cart's position. It is observed that although both the controllers are capable to control the multi output inverted pendulum system successfully; time varying periodic control delivers better robustness compared to nonlinear SMC control strategy by virtue of its loop zero-placement capability. Simulation study is done in MATLAB-SIMULINK environment and the responses are presented in time domain with detailed analysis.