The dynamic characteristics of the double-pad inwardly pumping water-lubricated spiral-groove thrust bearing (SGTB) is different from that of the outwardly pumping version, especially under a high-speed condition. However, no literature on this topic can be found up to now. In this study, a comparative study on the dynamic characteristics of the two types of SGTBs is conducted. First, a turbulent lubrication model considering centrifugal and cavitating effects for the double-pad SGTB is developed based on gas–liquid two-phase flow. The steady-state and perturbed Reynolds equations of liquid phase are derived using linear perturbation method. Subsequently, the boundary fitted coordinate system and control volume method are applied to solve the Reynolds equations. Then, the axial stiffness coefficients of high-speed water-lubricated bearings are verified by an experimental study. Finally, the influence of operating conditions and configuration parameters on the dynamic behaviors for the two types of SGTBs is investigated. The results show that the double-pad outwardly pumping bearing is superior to the inwardly pumping version in all the dynamic coefficients when the radius ratio exceeds 0.65. When the tilt angle exceeds 1.2 × 10−4 as well as when the eccentricity ratio exceeds 0.7, the dynamic damping, angular and cross-coupled stiffness coefficients of the outwardly pumping bearing may be larger than those of the inwardly pumping one.