Risk analysis of power networks under natural hazards requires a model of the power flow following initial failures in the network caused by the hazard. The model should include cascading failures through the network, for which different models have been proposed in the literature. Past studies have compared widely used models for assessing the performance of power networks, such as the topological, betweenness-based and power flow models, and found correlations among the model outcomes. However, they do not compare them for systems subjected to natural hazards, where other factors (e.g., seismic intensity and resulting ground motions) also affect the system performance. Ultimately, the choice of the appropriate model depends on the analysis purposes, the type of power network (e.g., transmission vs. distribution), the available amount of information, and computing resources. In this contribution, we investigate the effect of the cascading failure model on a seismic risk evaluation. To this end, we perform numerical investigations on the power network in the central coastal area of Valparaíso Region, Chile. Specifically, we compute and compare loss-exceedance functions for two models: Origin-destination betweenness centrality (ODBCM) and DC linear power flow (DCLPFM), for different representative seismic scenarios. We also compare the models with and without considering the uncertainty in the ground motion field.