I'm not sure how reliable princeton review is but it says it on their website FAQ
http://www.princetonreview.com/medical/mcat-faqs.aspx
Apparently they aren't too reliable. taken from AAMC website since people want to argue over an internet forum when it doesn't matter who the bleep scores the WS anyway.
Writing Sample Section Score
The Writing Sample section is scored independently. There are two essays on the exam. Each essay is scored twice on a scale of 1 to 6, with 6 being the high score. The resulting four scores are summed to result in the raw score. This raw score is converted to an alphabetic scale ranging from J (lowest) to T (highest). Note that the sum can result from different combinations of individual scores. For example, a student whose scores are 4 and 5 on the first essay and 4 and 4 on the second--a raw score of 17--would receive the same alphabetic score point as student who scored a 3 and 3 on the first essay and a 5 and 6 on the second.
ScoreTypical Characteristics of Essay 6 Esssays that score 6 show clarity, depth, and complexity of thought. The treatment of the writing assignment is focused and coherent. Major ideas are substantially developed. A facility with language is evident.
5 Esssays that score 5 show clarity of thought, with some depth or complexity. The treatment of the rhetorical assignment is generally focused and coherent. Major ideas are well developed. A strong control of language is evident.
4 Esssays that score 4 show clarity of thought and may show evidence of depth or complexity. The treatment of the writing assignment is coherent, with some focus. Major ideas are adequately developed. An adequate control of the language is evident.
3 Esssays that score 3 show some clarity of thought but may lack complexity. The treatment of the writing assignment is coherent but may not be focused. Major ideas are somewhat developed. While there may be some mechanical errors, some control of language is evident.
2 Esssays that score 2 may show some problems with clarity or complexity of thought. The treatment of the writing assignment may show problems with integration or coherence. Major ideas may be underdeveloped. There may be numerous errors in mechanics, usage, or sentence structure.
1 Esssays that score 1 may demonstrate a lack of understanding of the writing assignment. There may be serious problems with organization. Ideas may not be developed. There may be so many errors in mechanics, usage, or sentence structure that the writer's ideas are difficult to follow.
Must be one effing smart computer to analyze if an argument is cohesive with examples, etc. If computers are that smart, they should eliminate English teachers everywhere.
So I don't know - trust AAMC who actually writes the exam or a stupid prep company with multiple errors in their practice materials and practice exams that barely resemble the real deal? You decide.