I thought both the 2007 and 2009 ADA test were pretty similar to the real exam on all sections. Some people say the OChem section is easier on the 2007 but I scored the same on the 2007 as I did on the real exam.
The 2009 is slightly harder especially on the QR but my scores were pretty close to the 2009 as well.
I would say the bio section on the real test for me was a little more random then both the 2007 and 2009 and so I scored a couple points less then I had on the practice tests.