One scientist (also a VW enthusiast), did a lot of spectral and other analysis of the new Mobil 1 with SuperSyn and the Tri-Synthetic and some other oils. You can see a lot of charts on this thread
If you read the whole thread, one person there is a Mobil distributor (you will have no problem identifying him). He will only make (wrong) general comments but never mention specifics. He still believed (or intentionally mudding the water) that the Tri-synthetic is 100% PAO based, therefore the new with SuperSyn is also 100% PAO based.
I quote one result. This is a volatility kind of test and the viscosity of the synthetic oils used in the test is 10W-30. It measures the temperature at which the oil loses 10% (by weight).
Temperature at 10% weight loss (°C):
Quaker State full synthetic 229.9
Mobil 1 SuperSyn 235.2
Valvoline SynPower 237.0
Castrol Syntec 238.6
Mobil 1 Tri-Synthetic 240.5
As you can see, the old Mobil 1 Tri-Synthetic was better than the other three synthetic oils, now the new Mobil 1 with SuperSyn is beaten by two of the other three. This correlated very well with the 15 deg F drop in flash point of the new Mobil 1 with SuoerSyn compared to the Mobil 1 Tri-Synthetic.
Interestingly, Castrol Syntec is the least volatile among the 4 oils. It seems Mobil has a lesson to lean from Castrol on the art of substituting.