Topscore and Kaplan are more similar to the actual DAT, but I think the real one is actually easier than all these practice materials. The real one definitely is easier than Barrons.
I was freaking out when I was doing the Barron passages, I thought I will get the things in the same difficulty.... But for me Barron was pretty much useless except the PAT part.
But you never know, I might get lucky in my actual DAT... maybe someone will tell you differently. But I don' think you have to worry too much