Some people say that its much harder and that might be true. For me it wasn't the case. I thought it was comparable in terms of difficulty but you definitely get more tone/inference Qs on the real DAT.
I think it depends a lot on which version of the exam you get. On mine, topscore pales terribly in comparison to achiever, only because every question in Topscore asked for answers that were found almost word for word. On the real exam, you might find half the answer in paragraph 2, and then the other half of the answer in paragraph 6.
Like, for example, you have a passage on dinosaurs. The third paragraph tells you that a tyrannosaurus rex is a bipedal carnivorious poikilotherm. Then it goes on to talk about plant eating dinosaurs for 2 paragraphs. Then the 6th paragraph introduces the velociraptor and say they are carnivorious homeotherms. The 7th paragraph states that all carnivorious homeotherms back then ate only birds. Then the 8th paragraph says all carnivorious poikilotherms ate only fish. The question will be like, according to the article, a tyrannosaurus rex's diet consists mostly of? (Yea i know this is incorrect, but you get the idea).
You'll actually have to READ to get this answer right. In topscore, all you have to do is look for tyrannosaurus rex in the passage you will find like, "The tyrannosaurus rex's diet consisted only of fish." Big difference for people who rely solely on search and destroy. People who can read and remember where certain stuff are located at, even if they dont remember every little detail, are at an advantage here. You remember where the food section is, and you go there but don't remember if a TRex is a poikilotherm or a homeotherm, but you also remember where the TREX section is too, so you're in luck! If you use SnD, you find Tyrannosaurus rex, but can't find their diet, and then you start to panic, and before you know it time is up lol. Yea...