Hello student,

First let me tell you to about the major difference between the two topics- The main difference between valence bond theory and the molecular orbital theory is that valence bond theory explains the hybridization of orbitals whereas the molecular orbital theory does not give details about the hybridization of molecules. Moreover, Valence bond theory describes bonding as a consequence of the overlap of two separate atomic orbitals on different atoms that creates a region with one pair of electrons shared between the two atoms.

Hope it helps..