Among "Effective Altruism" rationalist circles, some of them prefer eating beef because a single cow produces a lot more meat than a single chicken, hence less suffering-year units per kilo of meat.
Sadly, growing cattle costs enormous amounts of food that could also feed people. And they seem to contribute quite a bit to greenhouse gasses. So eating beef may be better than eating chicken when it comes to animal welfare, but worse when it comes to the environment.
Best just eat less meat in general.
That depends. Sometimes it is true, sometimes it isn't. People can't eat grass, for instance.