They are very comarable. I did really well on the final, but I did better on the orgo and gen chem sections on the DAT. However, I did worse on the RC and QR than on the final. I really think when you get to a certain level of practice it depends on the particular test you are taking. Like if you get a RC passage that you already know a lot about, you will probably do better than on a different passage. Likewise, if you get a series of not-too-hard math questions on one test, you may get a not-so-nice set of questions on another test.
I think it's a probability thing. The probablility of you geting a similar score is very high, but there is a small possiblity that you get a lower or higher score as well.