There are two pages analyzing the popular character, word, and phrase counting software out there. The comparison pages can be found at: mywritertools.com/information.asp They all tend to report slightly different numbers and the comparison tries to indicate why the totals are different.
myWordCount has just been released for Mac and Windows, and it will import Scrivener project files and do word, phrase, and sentence length analysis on the content. Makes it easy to find overused words and phrases, or sentences that are just too long or hard to read.