One of the major issues surrounding the research and development work involving hybrid electric and fuel cell vehicles (HEVs and FCVs) is their overall efficiency of converting the input fuel into actual work at the wheels of the vehicle. The main idea behind efficiency comparisons between HEVs and FCVs is the analysis of their respective well-to-tank (WTT) and tank-to-wheels (TTW) efficiencies, the product of which reveals the well-to-wheels (WTW) efficiency, which is one of the deciding factors for technology acceptance. This paper primarily aims at presenting critical comparative issues with regards to the overall efficiencies of the most popularly proposed HEV and FCV topologies. Finally, the overall efficiency analysis performed in this paper will lay down the foundation for a concrete conclusive comparison between advanced vehicular topologies of the future.