Recent clinical trials have demonstrated the feasibility of using implantable neural stimulators for advanced therapies. However, to reduce long term deterioration of biological tissue, the amount of injected charge needs to be limited. Also, the stimulation has to be energy and power efficient to reduce battery dimensions and to maximize its lifetime. Several studies demonstrate that rectangular stimuli are not optimal regarding those criterion, and alternative waveforms have been proposed. In this report, a comparison between conventional rectangular stimuli and sinusoidal excitation is presented. We used in-silico models and in-vivo rodent experiments to determine excitation thresholds and injected charge per phase for both waveforms. Both studies demonstrated that sinusoidal stimulation required less injected charge per phase, thus suggesting that it is a safer paradigm. Peak power analysis does not provide any indication in favor of rectangular stimuli or sinusoidal stimulation. On the other hand, the stimulus energy plot demonstrates that sinusoidal excitation is globally more energy efficient than the traditional rectangular pulse and identifies an optimal stimulation zone.