When to use which turningtechnique?
In cycling, there are different ways to take a turn.
Now, which technique do you use for what curve?
Follow your head/horse and carriage
If you ride at low speed and you want to turn, you cannot do that with body and bike in a sloping position. You would fall. You turn with body and bike upright, turning your steer and turning your head.
Classic turns are often used in a gentle curve in the track, which you’ll have to take often, such as in a criterion. At some point, you know exactly how fast you can go through the turn and how much you should bank. And even which one you can peddle through, and which you you cannot.
Use the skiturn in sharper turns. Even if the curve extends farther than you expected, you can use it to provide additional pressure to keep the curve. Especially in a descent that can come in handy :).
In courses where you encounter curves only once and so you do not know them well, you can make adjustments faster with the skiturn.
The difference between the classic bend and skiturn is elaborated upon in: http://www.fiets.nl/forum/viewtopic.php?f=14&t=1757
Also included are comparisons with skiing, skating and motorbike racing. In Dutch.
Of course you need to see the classic Cancellara descent, with beautiful music of Mozart.
Crashes and various cornering techniques
It is difficult to determine which cornering technique works better to avoid a crash. You’d have to test, but how? So you have to do with the analysis of real-live crashes. From near-crashes, much greater in number, you can also learn a lot. Just do not stop with: “Phew that was close, such bad luck, just that car right there”, etc., but try to learn from it. Ask yourself “What could I have done differently and better in a similar situation?”, and ‘How do I master such a response better?”
In Crashes there are a few videos of crashes from professional races with an analysis of what (possibly) went wrong, and what the rider could possibly do better to lower the change of crashing.
See also learn the difference between unconscious and conscious: Learning