In the present work, we aim to understand the impact of density functional on the predicted ORR activity of 3d-metalloporphyrin catalysts. We calculate scaling relationships and theoretical overpotentials using six popular functionals that span different levels of approximation and compare results against the efficient coupled cluster variant DLPNO-CCSD(T) (Domain-Based Local Pair Natural Orbital Coupled Cluster with explicit Singles and Doubles excitations and a perturbative Triples correction). In doing so, we expand upon the work in Ref 12 by using large basis sets and dispersion corrections throughout, investigating the double-hybrid B2PLYP, and focusing on metals relevant for the ORR (including iron porphyrins). In addition, we scrutinize the sources of discrepancy between the functionals considered here, including the identification of ground spin states, geometry optimizations, and empirical gas-phase corrections.