Bio part: actual DAT covers more topics than topscore or kaplan test, so kaplan book is not enough, maybe you need some mcat bio book or text book for reference
Gchem Ochem part: actual DAT is easier than topscore, less calculation, but more thinking. Ochem is also easier. so kaplan book is enough for you to score 20+
PAT part: i dont know whether its easier or not, but i scored between 19-21 on topscore
RC part: easier than topscore, i think. more like the kaplan tests. but the article is longer, so you need more time to finish reading
QR: not so many probability questions, but the rest is just similar to topscore's