I have been a vegan for five years, before that I was a vegetarian for four years. As far as health goes, I feel that my health is basically the same comparing to the times I was an omni and a vegetarian. I do not feel any sort of health differences personally.
Personally I am a vegan for ethical reasons. I feel that veganism is further rejection of violence. It's a position against enslavement and exploitation of nonhuman animals. Being a vegan, to me, is about acknowledging basic rights of sentient beings. I am a vegan because I do not believe in unnecessary suffering and I do not believe that human beings need to eat anything from animals, therefore eating animal products contributes to unnecessary suffering.
I am not Buddhist so I can't really relate it to anything like that, it's just a moral choice I made on my own.
"My actions are my only true belongings." Thich Nhat Hanh