SD2007,
I know I'm not Erin and that's who you asked, but for what it's worth, I think the Kaplan book is far superior to the Barron's book. In fact, if I were you, I would definitely use either the Kaplan or the Princeton Review book instead of the Barron's book as a supplement to the official SSAT test prep book -- which, as Erin says, there really is no substitute for.
Granted, I have not worked out of the Barron's book for a couple of years, but that's mostly because the last time I did so, I was appalled by the number of errors, the way the book was laid out, and just how poorly the questions mirrored those in the official SSAT prep book. So I'm basing my review on that, and it could have changed...