This thread may be outdated but I'll post anyway.

I've read both books as well. I found the plans to be a little different. For instance, the PPLP included 3 plans, the Hedonist, the Dilettante, and the Purist plans whereas the older book did not. Basically, the PPLP is based on newer research so I would recommend that you follow PPLP.

Also, the PPLP seems more geared around health management. They advocate eating only organic foods and staying away from artificial sweeteners and processed foods. Also, they take a stronger position on taking antioxidants and other supplements. They also have very interesting information about the harmful effects of iron. Lastly, they have the best description about insulin resistance that I have ever come across. I enjoyed PPLP more.

Hope this helps,
Wanda