The predicted boiling point of a substance with both London dispersion forces and dipole-dipole interactions will be higher than that of a substance with only London dispersion forces. This is because the presence of dipole-dipole interactions, which are stronger than London dispersion forces, will result in stronger intermolecular forces between the molecules. Stronger intermolecular forces require more energy to overcome, leading to a higher boiling point for the substance with both types of forces.