Ok so lets just run this down and get everyone clear on this...

Push briefly, the "4x4 triangle !" light illuminates (same light as every other BMW minus the 4x4 text on the bottom). Pushing briefly turns off DSC, but leaves DTC on. DTC or dynamic traction control allows for a little more fun and wheel-spin before the car will react putting you back on the road. Think of it a delayed and less intervening DSC.

Holding the button for 5-8 secs, turns DSC/DTC off completely meaning you are on your own. The car will not intervene whatsoever.

Now, its a little different on our cars than other BMW's because of xDrive. It is very difficult to get more wheelspin and have more 'fun' (i.e. tailhappy sideways turns) because xDrive simply counteracts it on its own. There is no way to turn off xDrive. Therefore with DSC/DTC off you can't really do that much damage to your xDrive BMW, but say if you were in a regular BMW sedan or convertible oh the tailhappy times you would enjoy...

Now, on another note, newer gen BMW cars label the button DTC (which makes more sense), as a brief press will switch the car into DTC mode. But the button works in the same way as in our cars...