One thing to keep in mind is that in general, as the specs get tighter, it tends to squeeze out any real differences between oils. Take Chrysler ATF+4 for example. The spec is so tight that there's effectively no difference whatsoever between brands (I think maybe they require a specific additive package).
And the modern-day VW specs are fairly tight as oil specs go, especially if the oil has to meet several of them. So I suspect the differences between LiquiMoly, Total, Mobil 1, Castrol and all the rest of the VW-approved oils are so minor as to be inconsequential.
API SN is a much less tight spec, so there's a lot more room for differences between oils.