Here is a great article on both the Vegan and Paleo approaches - read the comments too. My comments are below:
The bottom line is both Paleo and Vegan groups are passionate about healthy eating habits. My personal bias is Paleo because of my autoimmune disease called Achalasia. Since my esophagectomy in October 2010, I have been full on Paleo with incredible success.
A few comments:
1. Vegetarians and Vegans (at least those making up my patient base over the last 26 years) eat WAY too many grains and not nearly enough vegetables. As a Paleo proponent, I eat more veggies than most of my vegetarian/vegan patients.
2. Paleo does not have to be low carb. If you are working out with any intensity at all (more than just taking a walk daily) you will most likely need more carbs than what veggies can supply. I choose not to eat grains of any type (I can eat rice once a week) as I have experimented on myself and just don't do well with grains. I choose sweet potato, yams, turnips, parsnips. The harder I train, the more I need these foods to recover.
3. Paleo does not have to be super high protein. If you are training hard, I would argue that you will benefit from higher protein (good sources of course as per the article) and I do benefit myself. Read this post by Nora Gedgaudas about protein and Paleo
4. Here is a great article with a menu plan from the different Paleo/primal approaches
5. Most Vegans/Vegetarians are going to be nutrient deficient. These deficiencies (Mg; Zn; Vitamin D; Omega 3's - sorry, flax seeds, etc. do not convert efficiently to DHA; B12) can take time to show up.
6. Everyone owes it to themselves to do a bit of personal experimentation. Discover what works for you and get healthy!