The complete set of MX2 and MX4 (M = C, Si, Ge, Sn, Pb and)( = F, Cl, Br, I) group 14 halides are studied with density functional theory and quasirelativistic effective core potentials. To analyze the role of density inhomogeneities and the asymptotic behavior of the Kohn-Sham effective potential in these molecules, the following exchange-correlation energy functionals are tested: local, semilocal (generalized gradient), and hybrid functionals. For comparison, Hartree-Fock results an also presented. Fully optimized geometries are in very good agreement with experimentally available data and with ether high-level theoretical calculations. The energy differences associated with the dissociation and disproportionation reactions are reported. Zero-point corrections and atomic spin-orbit effects are included in these reaction energies. The dissociation energies predicted at the Hartree-Fock level are underestimated, the local energy differences are overestimated, and both the semilocal and hybrid approaches provide the best estimates for these reaction energies. The disproportionation energies, which are commonly used to explore the relative stability of different atomic valences, show a behavior that departs from that commonly known for reactions involving a single atom: the local and semilocal disproportionation energies have very similar values and follow the same trends.