There is very little difference between VG5 and VG10 steels. The main differences are VG10 contains less vanadium giving it a finer grain content. Also, VG10 contains cobalt to help improve the toughness lost by the lower vanadium content.
It is highly inadvisable to choose a knife based on steel type, especially not ones that are as similar as VG5 and VG10. It’s also pointless to try to rank one as better than the other. There are other factors like geometry, heat treatment, handle design, fit and finish that are just as important to the quality of the knife. The heat treatment from one factory can easily render VG5 much harder than VG10. The specs for each steel would dispute this, but the specs do not take into consideration the differences among manufacturers in their heat treament. The specs only speak to the maximum attainable hardeness in a perfect world.
Handle design and fit and finish also vary greatly among factories. Even within the same brand the geometry of a blade can be different. Differences in geometry can also result in differences in weight. Take a look at the Tamahagane SAN Tsubame knives. These knifes do not begin to taper until the line where the hammered effect stops. This different taper gives the SAN Tsubame knives a greater weight than the SAN knives. The greater weight appeals to alot of people. This factor should be given greater importance in a buying decision than whether the knife is made of VG5 or VG10 steel.
As previously noted, VG10 steel has a finer grain content. This is very noticeable when you go to sharpen a VG10 knife. The finer grain content prevents the blade from really grabbing the stone to bring back an edge. It also creates a very fine white powdery residue on the stone which just doesn’t seem like steel to me.