Honestly, I took the MCAT not too long ago. Comparing it with the DAT practice questions and hearing some from past DAT takers, I think DAT Bio questions are tougher. They are more direct discrete questions. MCAT has some discretes, but focuses more on passage-based questions where you are required to combine the knowledge from the paragraphs provided and your basic bio knowledge to answer the questions. On the DAT...you either know it or you don't!
I'm planning on taking the DAT soon and using my MCAT material is great! Covers nearly the same subjects. Truthfully...the high scores always come from practice, practice, and more practice! lol
I hope that helps 👍