Most effective altruists would agree with you (and thus disagree with a possible takeaway from Chik-Fil-A's advertising) that eating chicken is better than cows, as cows provide significantly more meat than a chicken, with ratios being up to 50 chickens per every 1 cow, as far as quantity of meat for normal portions go. In other words, someone eating only chicken may kill X chickens, but someone eating only cows may kill 1/50X cows. Of course there are other variables involved like weighing the differences between these animals, their treatments, lifespans, etc., but it is nonetheless a point with notable weight. Although this isn't quite the area I was getting at, just that the most significant things should be looked at first, all else constant.
