Barron's tends to be much more detailed. Princeton Review focuses on the main concepts. If your teacher was a good one, go for PR. If not, Barron's. Both are great books. Study a lot of past AP's from collegeboard. They REALLY help.
Kaplans and Barrons are good for AP chem-I got a four. Try to mix up what you use so you don't get used to 1 test writer. Also, check out the college board website-they have old free response questions and answers.
Kaplans or Barrons study guide-I checked both out of the library-I practically owned them for a month and saved myself $30. Also, check out past free response on the college board website-they helped me get a 4 in Chem. You need practice taking the test under timed conditions.
For AP bio, I would definitely recommend Cliff's. Also, as someone else suggested, check out the collegeboard website for free response questions from past years. They also include the grading rubrics, which I found the most useful when studying for the AP last year.