The configurations of a series of short polar model molecules for poly(vinyl chloride), PVC, and poly(ethylene oxide), PEG, have been determined from extensive molecular dynamics simulations of the corresponding bulk melts. Their conformational and configurational properties are compared to those sampled for the same models by a pivot Monte Carlo procedure based on the assumption that chain configurations in the melt depend only on highly localized near-neighbor intramolecular interactions. The comparison proves favorable for all neutral and polar chains, with the exception of the realistic model leading to the gauche effect in PEG. Discrepancies in the latter case are related to the failure of the single-chain local energy approximation to account for the specific competition between intramolecular "1 ... 5" C-H ... O and intermolecular C-H ... O electrostatic interactions in the PEO bulk melts.