Reference states for molecular orbital energies in DFT calculations
In molecular electronic structure, electronic/orbital energies are measured with respect to an energy zero of an isolated electron in free space.

Hence a lower LUMO energy does correspond to an orbital that is more apt to accept an electron/a more negative electron affinity compared to another molecule.

Correspondingly a higher HOMO energy corresponds to an orbital that is more liable to give up an electron/a less positive ionisation energy compared to another molecule.

This is the basis of Koopmans' theorem in Hartree–Fock theory and it's equivalent in DFT.