I don't think it's really that clear-cut, particularly when the animal-welfare and planet-welfare arguments get intertwined:
"A number of past studies have found lower greenhouse gas emissions associated with the feedlot system. One reason is that grass-fed cows gain weight more slowly, so they produce more methane (mostly in the form of belches) over their longer lifespans...
To many grass-fed advocates, this is one of the main reasons for switching to grass-fed beef. After all, cows evolved to live this way."
"A number of past studies have found lower greenhouse gas emissions associated with the feedlot system. One reason is that grass-fed cows gain weight more slowly, so they produce more methane (mostly in the form of belches) over their longer lifespans...
To many grass-fed advocates, this is one of the main reasons for switching to grass-fed beef. After all, cows evolved to live this way."
https://www.npr.org/sections/thesalt/2019/08/13/746576239/is...