In the LS state, while the DE(oxo) reaction energies for Fe and Ru catalysts are close (average values of -23 kcal/mol and -28 kcal/mol, respectively), oxo formation is slightly more favorable for Ru. However, in the IS and HS states, the favorability of metal-oxo formation in Ru catalysts over Fe catalysts becomes much more pronounced (on average by ca. 22 kcal/mol in the IS state and 31 kcal/mol in the HS state, Figure and Supporting Information Figures and). On average, we find that Fe catalysts have larger metal-oxo bond orders and shorter metal-oxo bond lengths compared to Ru catalysts, which would normally be indicative of greater stability of Feoxo species over Ru-oxo species (Supporting Information Figures and). Instead, our findings indicate that differences in metal chemistry are not well captured by these electronic descriptors, and the relative metal-oxo formation favorability is significantly influenced by the spin state of the metal. In all three spin states, we find that HAT is more favorable for Fe catalysts on average (by ca. 9 kcal/mol for LS, 5 kcal/mol for IS, and 9 kcal/mol for HS states) than for Ru catalysts (Figure and Supporting Information Figures and). Interestingly, Ru catalysts predominantly have positive DE(HAT) values in higher-spin states (i.e., 2-26 kcal/mol in the IS state and 5-23 kcal/mol in HS states). Indeed, contrary to the trends observed in the DE(oxo) values, the disparity in Fe and Ru DE(HAT) values does not become more pronounced with higher-spin states but remains consistent (Figure and Supporting Information Figures and).We note that we select the optimal radical-coupling convention for both metals during HAT (i.e., a-radical transfer for Fe catalysts and b-radical transfer for Ru catalysts) as informed by prior literature as well as the spin splitting energies of the metal-hydroxo species (see Sec. 4b), but we still observe more favorable DE(HAT) values in Fe than Ru catalysts (Supporting Information Figure ). Taken with the trends in DE(oxo), this would suggest that selecting a catalyst spin state to target favorable DE(oxo) in Fe or Ru will have a limited effect on DE(HAT) values, suggesting weak trade-offs between these two steps, which we will explore in more detail next.