I chose quail over chickens for a few reasons.
1. They are not particularly loveable. I have Texas A&M's, fourteen of which I hatched and three I bought before I decided to go the meat route. I harvested one already, and although it hurt, we'd never really bonded--I'm the food monster, and they only really do three things: Stand there, walk around, and sit. It is easy to look at a quail, harden my dumb soft heart, and remember that he is a resource to be treated with care and respect, not an individual who must be loved and protected. Chickens, on the other hand, are cuddly and individual and funny and I know I'd get to like them and then I could never eat them.
2. They are fairly anonymous. I have no idea which quail is which. So at the harvest, I don't know who this bird is as an individual, I have no fond memories of him or her, and I can love my FLOCK but not THIS BIRD.
3. They are very physically easy to slaughter. Pull and twist. Then take the head. Then defeather, defoot, and it has become meat and not the animal it used to be. Chickens are bigger, have more blood, might take longer to pass, and would be more physically difficult so not as sure for me, a relative newcomer to this.
4. They are easier to raise in my backyard in greater numbers. Five chickens = few enough chickens that I'd know them. Forty quail = my flock, none of whom I recognize. And no smell in deep bedding.
5. They are absolutely delicious. I've always liked quail more than chicken anyway.
I've got a second generation line of James Marie Texas A&M's, for reference.