You have to define 'optimal' before that can be answered. Or at least specify 'optimal for whom.' Typically, Paleo is considered more orthodox, closely approximating foods that were available to Paleolithic man. Primal is less averse to Neolithic foods and attempts to achieve the same (or even better) results metabolically.

I thought Melissa made an awesome graph that illustrates some of the differences and similarities quite clearly.

I'm currently experimenting with the PaNu section. I also plan on switching from dairy to tallow and more of other animal fats at some point to see if eliminating dairy is more optimal for me.

Bottom line: if someone simply eliminates from their diet the items that are common to both diets 'do not eat' list - starting with sugar, wheat and other grains...a huge step toward optimal will have been taken. The remainder is achieved with experimenting at the individual level.

Which is optimal is a hornets nest of subjective opinion

I'm more in the PaNu/Hyperlipid camp, Cordains paleo and Marks Primal both hold flaws, but both are marketing widespread and can't be as strict in recommendations

http://www.marksdailyapple.com/whats-the-difference-between-primal-and-paleo/

Mark sums up the differences in the above link in his opinion

Saturated Fat, artificial sweeteners etc.

What is optimal nourishment for one might cause troubles for another.

A few thoughts that come to mind.

The optimal diet for any one person depends on:

• that person's sex, age, health parameters, such as: allergies or food sensitivities/intolerances, genetic make-up, health/medical history: including the history of illnesses, allergies and other ailments in his family, going back for several generations.

• that persons' budget, goals, habits, preferences, etc.

Some find they do better with more carbs, some fewer, some as few as possible. Some do better with butter, cream, yoghurt, or even cheese. Some have problems with casein, lactose, opioids, or can only use those foods from certain breeds of cows. Some can drink raw milk, but not pasteurized.

Other examples, to name just a few:

Plants have anti-nutrients. Meats have amines. Coffee and chocolate can trigger allergic reactions. Tea and coconut have salicylates.

The list of what one might not be able to eat or drink is endless.

Each one must experiment, read, and choose for himself.

It is grand that there is no such thing as one size fits all.

I wish you all the best in choosing what fits you.

The main difference between the two is Primal allows dairy. For me primal works well - I love dairy. For my hubby paleo works better - he's slightly lactose intolerant.

For someone trying to gain weight, primal would have a slight edge - you can do GOMAD

For someone trying to lose weight, paleo would have the edge - dairy tends to help in weight gain.

Mark Sisson came up with the primal name, I think probably to differentiate his approach from Loren Cordain's.

Kurt Harris, in his updated Get Started post, is calling his approach pastoral, to reflect that he allows dairy. The dairy might be from cows, sheep or goats. This is the food that would have been eaten after animal husbandry, but without agriculture.

I think it better to therefore define the dichotomy as paleo/pastoral. What's optimal really depends on how much you want or need to eat dairy products.

I realise this doesn't answer the question, but I hope it helps you think better about it.

Primal promotes the use of yogout. I understand Mark's point, that the probiotics gives your gut a fighting chance at mainitaining a heathy flora. For most people the intestinal villi has been dessimated by grains which act like sandpaper. The porosity of the gut membrane and dairy is also a concern. Nutritional malabsorption, and dealing with the superglue of glycoproteins in the cardiovascular system and nervous system are a great cause for concern. My issue is simpler then that though. Being pre-diabetic, yogout has a high glycemic value, a negative effect on the pancrease, as well as being another acidic food your digestive tract has to deal with. I would tend to side with Loren Cordain on many of these issues. Having an autoimmune disease predisposes you/me to the difficulty in dealing with the glycoproteins, lactose and glycemic factors in yogout. But I love them both for holding tenaciously to the tenants of the superiority of the hunter-gatherer diet and lifestyle.