Hydraulic legged robots play a key role in rescue and exploration missions due to their characteristics of high dynamic, high burst, and high terrain passing ability to complex terrains. Leg units, the main part of robots, are key determinants of robots’ motion performance. The actuation types of the leg unit joints could influence the motion characteristics. According to the different actuation types at the hip and knee joint, there are four configurations: dual linear cylinders (LL), dual rotary cylinders (RR), a combined actuation of linear and rotary drives (LR), and the corresponding reverse configuration (RL). The state-of-the-art (SOTA) hydraulic quadruped robots commonly adopt LL and RL configurations to design leg units. However, there is no quantitative analysis of these two configurations in the field and conclude which one is the optimal configuration. This study employs Amesim simulation technology to conduct a detailed quantitative analysis between the LL and RL configurations under different motion conditions. The results show that the RL configuration leg units require less hydraulic flow rate during all motion conditions and the advantage is even more pronounced at high speeds. Also, the energy loss of valve is less with the RL configuration. In conclusion, this study not only confirms the RL configuration is optimal but also gives the basis for selecting the design configuration of the leg unit of the Spurlos II quadruped robot.