For pK(a) prediction of aliphatic amines (amines relevant to industrial CO2 capture), the performance of quantum-chemistry continuum-solvation methods is contrasted with the 1981 pencil-and-paper group-additivity method of Perrin, Dempsey, and Serjeant (PDS). We have optimized a quantum-chemistry continuum-plus-correction strategy, as well as updated the parameter values in the PDS method. The PDS method outperformed the continuum-based method: root-mean-square errors for a sample of 32 amines are 0.28 for the continuum-based method, 0.33 for the original PDS method, and 0.18 for the updated PDS method. Considering also that there is ambiguity in choice of cavity radii and molecular conformer for continuum-based methods, we recommend the pencil-and-paper PDS method over such methods.