Fuchs do make great oils. Silkolene/Titan Race is really good stuff but VAG have always worked with Castrol for engine and gear oils, unless that's changed recently?
Got no problem using their engine oils, but the O2Q gearbox is notoriously picky with oil. The VAG oil has been proven by lab analysis and day-to-day use to be the best there is.
It may be just as good, potentially, the price difference isn't big enough to justify moving away from what I know works, on a whim, only for it to be crap and have to drain it and put VAG oil back in again. Not worth the hassle.