In this paper, hybrid BCI that merges Event Related Potentials (P300) and Steady State visual Evoked Potentials (SSVEP) simultaneously is proposed to enhance the performance of Four-choice command system. Here we integrate human facial structure in external visual stimulus to evoke stronger cortical responses in hybrid SSVEP+P300 BCI & compare it with non-face stimuli. We also addressed question of feasibility of eliciting one potential by face & other by non-face stimuli. To evoke SSVEP & P300 responses, paradigms with non-face stimuli, neutral face stimuli, and facial expression changes stimuli are proposed. We also projected additional paradigm where SSVEP is elicited by non-face and P300 by flashing different facial expressions. Results proved the last paradigm evoke stronger cortical potentials and thereby improve system accuracy and ITR than other paradigms. Author discussed external stimulus parameters that might affect simultaneous evocation of multiple brain potentials and their deterioration effect on individual potentials.