Uncertainty in land model projections remains persistently high and the relative roles of parametric and structural uncertainty are difficult to disentangle. To compare parametric sensitivity across model structures we present two parameter perturbation ensembles (PPEs) using the Community Land Model version 6.0 (CLM 6.0) both operating in satellite phenology (SP) mode. The ensembles contrast two vegetation modules: 1) the default CLM vegetation module and 2) the Functionally Assembled Terrestrial Ecosystem Simulator (CLM-FATES). We perturbed 204 CLM parameters and 137 FATES parameters spanning canopy, soil, and snow processes, and quantified their effects on biophysical fluxes globally and across biomes. Most parameters have minimal impact on global biophysical fluxes, with only a few substantially influencing model results. While CLM and CLM-FATES exhibit similar ensemble spread and parameter sensitivity for some fluxes, CLM-FATES shows substantially larger spread in gross primary production (GPP), driven primarily by strong sensitivity to top-of-canopy carboxylation rate (Vcmax). Compared to CLM, CLM-FATES also shows a weaker GPP response to soil hydrology parameters and exhibits higher water use efficiency. Cross-model comparisons reveal similar sensitivities for some parameters (e.g., leaf dimension) but divergent responses to others (e.g., stomatal slope and intercept), highlighting underlying structural differences between CLM and CLM-FATES. Differences in water use efficiency and sensitivity to hydrology- and stomatal conductance-related parameters underscore how model structural choice fundamentally alters parametric sensitivity. These results provide the first systematic framework for PPEs with CLM-FATES, and the datasets generated from these ensembles can be used to identify influential parameters and guide future calibration efforts.