Vegan.
1. Ethics. I don't want to cause unnecessary pain or suffering, either directly or indirectly.
2. Consistency. If I extend moral consideration to my fellow humans under principles X, Y and Z, It would be morally inconsistent to withhold it from other species to whom the principles also apply.
3. Environmental concerns. Animal agriculture uses massive amounts of water, generates massive amounts of pollution, particularly in factory operations, and generates more greenhouse gas/Co2 equivalent than automobiles.
4. Public health. Antibiotics used in animal agriculture contribute to the proliferation of resistant bacteria. I'm also concerned with zo-onotic diseases.
5. Ego-identity. Vegetarianism is considered a good thing in the status communities I identify with.