It has been dry long enough for me to make a couple of tests. Using my G-Tech meter I made some 0-60 runs. One with VDC on, one with VDC off, and the third after holding down the VDC button until the light turns off. There was no real difference in all runs. 0-60 times were between 6.974 and 6.984 seconds; only 1/100 of a second different. The maximum G forces were also close, .65 to .66 G's. The 1-2 shifts were exactly the same, 41 MPH, as well as the 2-3 shifts, 70 MPH. (I ran past the 60 MPH figure to be sure to have good 0-60 times). Max HP during the runs was at about 4,690 RPM, with max torque at about 3,840 RPM. The torque, speed, and HP graphs were essentially the same on all three runs. Temp was 88, high humidity, dry road, no tire spin.
From what I can see, holding down the VDC button until the light turns out doesn't do anything. I may do some other tests in poor traction conditions, both acceleration and braking, but I don't expect to see anything different.