MoonGlo,
In my opinion, I feel that the MCAT and the DAT are two almost entirely different types of tests. True, they overlap in a lot of the material that is tested, but the format/structure is quite different.
First, the MCAT has the following sections:
1. Biological Sciences (Covers biology and organic chemistry)
2. Physical Sciences (Covers physics and inorganic chemistry)
3. Verbal Reasoning (Reading comprehension/Critical thinking)
4. Writing Sample
The DAT has the following sections:
1. Biology
2. Inorganic Chemistry
3. Organic Chemistry
4. Reading Comprehension
5. Perceptual Ability
6. Quantitative Reasoning
The MCAT in my opinion is harder because it not only tests the depth of your knowledge, but also, it tests your ability to interpret complex, sometimes abstract passages and apply known information.
The DAT is more of an exam that tests a person's knowledge-base. Rather than present long and sometimes complex passages, the DAT presents short "Trivial Pursuit-type" questions followed by a number of answers. For the most part, it is a "you know the answer or you don't" type test. However, the Reading Comprehension and Quantitative Reasoning sections are two sections that don't apply to this theory and do test one's critical thinking ability.
To adequately prepare for the MCAT, I definitely suggest preparing 4-6 months in advance. For the DAT, I would say about 3 months in advance, however, I can already tell you that people are probably going to respond to this and say "WHAT!!!!!....6 MONTHS!!!!!!...I studied for the MCAT 2 weeks before the test and got an average of 12 and 13's on ALL sections."
Anyway, that's my info...
Racerdude