I'm not Heruklease (obviously, lol) but I can tell you what I think. I agree that CDR passages were on the more interesting side, but regardless if it's interesting or not, you have to be able to understand the author in order to answer CDR questions. On the real DAT, there will be a several questions where you will also need to understand the author. I had several questions that asked something like "The authors tone in this passage is what?" And then it lists absurd and ridiculously big adjective words. LOL. They were big words to me... I did not understand the vocabulary words of the answer choices. In the end, the real RC questions were harder than both. But if I can choose between Topscore and CDR, CDR wins by far.
Topscore, on the other hand, you don't even need to read the passage. It's ridiculously easy and it's all search and destroy questions (which were mostly in order of the passage). I had 2 science passages on the real RC.... which weren't very interesting to me. The third passage, however, was about exercising and I thought that was interesting. The font of RC passages on the real DAT is also BIGGER than Topscore.