Wheildon claims that fully justified body text (aligned flush-left and flush-right) is superior to flush-left/ragged-right alignment. Full justification creates even lines of text, which, according to Wheildon, makes for a smoother eye movement from line to line.
Conversely, ragged-right alignment creates uneven spacing at the end of each line, but the spacing between words is even. On the other hand, full justification causes uneven spacing between words. In other words, there is always the same amount of space, but one puts it after the line of text, while the other forces it between words. The following is an example of justified text. Notice the uneven word spacing.
Full justification also increases the number of hyphenated words. So, which should you use? There is no consensus on this point. Some magazines and newspapers justify the body text, while others use flush-left/ragged-right.
Most design decisions are subjective. There are only guidelines, not hard and fast rules. However, if you decide to justify the text, set minimum and maximum spacing between words to help prevent "rivers of white space" from cropping up between words.
In Looking Good in Print, Roger Parker cites other experts who argue that readability is improved by flush-left/ragged-right text alignment. They claim that even word spacing makes it easier for readers to recognize word groups.
Parker claims that many newspapers and magazines use justified type to increase word density and save money. He prefers ragged-right text because the open space at the end of each line lightens the appearance of a publication.