Automotive engineers and researchers have proposed different Series-Parallel Hybrid Electric Vehicle SP-HEV topologies. The Toyota Hybrid System (THS) is the most known SP-HEV based vehicle, but alternative solutions such as Electric Variable Transmission (EVT) have been also proposed. Efficient comparison between these different solutions is a key point in order to estimate the added value of each topology. This paper presents the application of optimal control to two series-parallel hybrid architectures for efficiency assessment purpose. The dynamic programming method is applied to the THS as well as to a virtual hybrid vehicle with an EVT. The way to take into account the supplementary degree of freedom provided by the decoupling of wheels and engine in both topologies is presented. The optimal fuel consumptions are then compared on different driving cycles and bring out an over consumption of the EVT topology. Then, a parametric study shows that inserting an appropriate gear ratio on the ICE shaft can improve the EVT efficiency that becomes close to the THS efficiency.