I think there is too much importance placed on the intelligence of the TCU, in controlling the two different AWDs. They both have the same two, basic jobs to perform.
1. Is to recognize a difference in wheel speed, above a fixed %, and to apply pressure to the clutch to stop it.
2. Is to apply a preemptive pressure to the clutch, to prevent the wheels from spinning. This is done according to the, throttle setting and the road speed maps, for all gears.
The type of AWD has little effect on the way the TCU does its job. The preemptive maps for both types, will vary, but I don't think it will be by much. We will have to wait till we can see a comparison of them to tell.
The TCU has no direct knowledge of the what the Torque split is, that is the result of the preemptive maps. Both types will apply a high pressure to the clutch when doing a full throttle start, to prevent wheel spin. The VTD will spin the back wheels just as easily as the Transfer will spin the front, if the clutch is not working. ( you only have to see the videos of the 'Boys from Brazil'
smoking the rears, to see, what the VTD is like without the clutch working).
When the car is in top gear and driving, the TCU can only work with the two inputs of throttle and speed, it does not know that the conditions that the driver sees would demand a different torque split, to handle them better. This is why there is a driver control on the 6 speed with the DCCD. so that the driver can input the other conditions that he sees.
So the question will be seen in a better light, when we can see the preemptive maps for both types and compare them.
Harvey.