Experimentally, there is no consensus to find out which of the α and β crystal phases of polyvinylidene fluoride (PVDF) exhibits the highest melting temperature. To unveil this ambiguity, we use an established procedure based on achieving the Gibbs-Thomson equation from molecular dynamics simulation on pure crystals and crystals containing 10% of regioisomerism defects. The rightness of the protocol is confirmed by the agreement with experimental data. We thus show that in pure crystals, it is the α form that exhibits the highest melting temperature. However, insertion of regioisomerism defects inside crystals influences more the value of the melting point of the α form than for the β crystal. The pure and altered β phase then show the highest melting temperature. This conclusion explains the experimental difficulty on finding which of the α and β crystal forms displays the highest melting temperature, since PVDF samples always contain regioisomerism defects.