According to Duden [***asymmetrisch***](http://www.duden.de/rechtschreibung/asymmetrisch) and [***unsymmetrisch***](http://www.duden.de/rechtschreibung/unsymmetrisch) are synonyms, but which one is preferable in a scientific context? What about other contexts?

Searching for the appropriate noun, I wonder why Duden knows [***Asymmetrie***](http://www.duden.de/rechtschreibung/Asymmetrie), but not ***Unsymmetrie*** - is the latter plainly wrong?