Grid Design Basics - The Graphic Design: Reference and Specification - page 53

Symmetry Versus Asymmetry
One of the first questions to ask when developing a grid system is whether a symmetrical
or asymmetrical grid is more appropriate. There are advantages to both, and the determi-
nation should be made based on the content and visual tone required for a particular
project.
A symmetrical grid is most often used for text-heavy topics or publications. It is an ideal
format to choose when one wants the most uniformity in a page layout.
An example of a symmetrical spread with margins set.
Asymmetrical grids are most useful when one wants layouts to vary across pages and when
there is a range of elements (images, footnotes, sidebar text, etc) that must be included in
a layout.
An example of an asymmetrical page layout with margins set.