In every approach I check FMGC VLS when in full flap, and compare with PDF¡'s VLS. Usually PDF's is two or three knots slower (safe side). Probably because the airplane is not as heavy as FMGC thinks, or who knows. Sometimes the difference is large and I immediately notice it during the flare (long, with relatively low pitch attitude)
But if PDFs is higher, then I add knots to the VAPP in the FMGC as necessary.
If in a given airplane the difference is always the same, there is something wrong with teh AoA probes or computers, and is wise to add knots to VAPP accordingly.