Of these, def2-ma-TZVP is by far the least expensive, adding only modest overhead upon def2-TZVP as documented in Fig. . In contrast, the upgrade from def2-ma-TZVP to def2-TZVPD improves the MAE for the S66 dimers by ≤ 0.1kcal/mol but nearly doubles the cost for the π-stacked uracil dimer that we use for timing benchmarks. The def2-QZVPD basis set improves the MAE by < 0.1 kcal/mol with respect to def2-TZVPD (although it does reduce some of the outliers), but increases the cost by nearly 5×. These disparities are exacerbated in Dunning basis sets, where the full complement of diffuse functions in aug-cc-pVTZ reduces the MAE by < 0.1 kcal/mol, as compared to jun-cc-pVDZ results, at 1.4× the cost, while quadruple-ζ basis sets provide very limited improvements over aug-cc-pVTZ at prohibitive cost. We recommend def2-ma-TZVP unless one is pushing for absolute convergence to the CBS limit, in which case Dunning basis sets provide slightly more consistent results.