Ok here is my take on it for whatever it's worth as I don't train people for a living anymore and when I did I was advocating the bb'ing type eating style of 6 meals a day...etc
We are comparing Zone 30/30/40 against paleoish eating(not strict paleo but just cleaner eating but not necessarily 30/30/40)
I looked over the comments and kind of find his "contest" a little bit ridiculous. How are you going to take 2 different people that need to get into shape with different diets and then declare victory based on who is leaner and performs better at the end? That would be assuming both these people have the same drive/determination/discipline and same work ethic and same just about everything else in order to determine if diet is affecting things.
For all he says about research/testomonials and all that, um what? For everything he points out you can find things that shoot that down just as quickly. For every great Zone athlete, you'll be able to find some paleoish athlete that is great too. It's been my observation amongst longer time CrossFitters that Zone works great....to begin with but a lot of people have adapted it from that such as the Athletes Zone which is way higher on fat blocks and lower on carb blocks. How can the 30/30/40 be magic if people don't end up sticking with that?
In regard to clients, I imagine you would have a easier time with clients sticking with cleaner eating than with the Zone, frankly because the Zone becomes a huge pain in the ass after a while. I think the Zone is great for learning portions and how much food is what but do I think a person NEEDS the Zone to get leaner? No, I think adherence and sustainibility should be just as important as short term results. If I went on the Zone tomorrow I know I'd lose some bodyfat...etc but would I be able to stick with the 30/30/40 Zone forever? Heck no. Been there done that. I think a person would have a easier time with cleaner eating as a lifestyle, eat proteins + veggies or fruit, if it has ingredients you can't pronounce try not to eat them. Cheating is done by both camps so we'll just assume there will be "cheat" days no matter which one you do.
Robb has some great stuff on his blog one post is here:
PM#30 has Robb's article about 42 Ways to Skin the Zone which has some good stuff too.
Hope this helps.