I'm not a fan of Kaplan. My friends have used Kaplan and liked it (possibly because it's easier than the actual test/doesn't reflect the actual test). That's just my opinion, though, others may disagree. IMO, Gruber's (particularly in math) > Barron's > PR
> Kaplan. I have all 4 and I like Barron's for its well-rounded difficulty. PR
has a pretty good imitation of real questions, and I suggest looking into their practice test book.