Originally Posted by doubleaught

The increase in accuracy from having 6MP on the same size sensor as your 12MP camera comes from each pixel being larger. Thus able to absorb more light and also less prone to various distortions.

So the quick answer is no, unfortunately you'll gain no quality from using a lower MP setting. The reason to choose a lower size is to gain a lower filesize if you aren't going to be blowing it up past a certain printed size. Other than his first line I completely agree with Zweiblumen's statements.

Hope this helps.