The quantitative assessment of seismic fragility constitutes a fundamental component of risk management strategies in seismically active regions. While the conventional maximum story drift methodology has been extensively employed for decades, the plastic strain energy criterion has gained prominence as a complementary approach, primarily due to its inherent capacity to account for the cumulative nature of seismic damage. This study presents a practical, comparative evaluation of these two damage indices for seismic fragility assessment of low- and mid-rise steel moment-resisting frames. Three prototype structures, comprising 4-, 8-, and 12-story frames, were designed in compliance with contemporary seismic codes and subsequently modeled using advanced nonlinear finite elements in PERFORM-3D. A suite of 20 near-fault ground motion records was employed to derive fragility curves via Incremental Dynamic Analysis (IDA) for two distinct performance levels: Life Safety and Collapse Prevention. The results demonstrate that, for the investigated structural typology, the conventional drift-based method yields consistently more conservative fragility estimates (indicating higher vulnerability) compared to the energy-based approach. For instance, at the Life Safety performance level, the spectral acceleration required to attain a 50% probability of exceedance was significantly higher when using the energy criterion. This observed trend, which contrasts with findings reported for taller building systems, underscores the significant influence of the selected damage index and specific structural characteristics on fragility assessment outcomes.