Barron's?>>>I have no experience with this.
DAT Destroyer?>>>Much more challenging than what you'll ever see on the real DAT. Nevertheless, this is a great tool to practice for the DAT.
Topscore?>>>The sciences and the RC are somewhat similar to the real DAT. However, the QR and PA are way easier than what shows up on the real DAT.
Kaplan?>>>The PA section is a joke compared to the real DAT. In science (Specially G-chem and O-chem), KAPLAN focuses a lot on concepts; whereas, the real DAT focuses more on problem solving and doing reactions.
Crack DAT PAT?