Paleo, I think it's more natural / suited to the human body (given that it's what we evolved on), and veganism is too strict for me, and you have to be careful with getting enough of certain nutrients. On the other hand, I saw an article the other day where someone was arguing against the paleo diet and pointed out that prehistoric people only lived to be about 30 years old. I doubt that's really due to their diet, though. Most Americans eat much worse and live much longer anyway. Also, one reason I might want to pick vegan is because eating animals and animal products is unethical because of the living conditions of those animals.