Suffering per kg from different meats

I've written before about how I try to eat flexitarian. Basically, I'm not 100% motivated/convinced by vegetarian or vegan arguments, but I'm not 0% motivated/convinced by them either, so I go somewhere in between.

One thing I've done, when I do have meat, is mostly choose chicken over pork/beef. I did this mainly under the assumption that chickens are probably less intelligent, or at least are biologically further from myself (the one being I can be 100% certain can suffer), so perhaps they suffer less. A secondary motivation was that beef creates more pollution than other meats.

But I just came across this estimate of how much suffering is involved per kg of a few different animal products. I don't know to what extent I agree with his calculations (yet (?)), but I've realized I've really failed to consider the size of each animal in my own thoughts for how to compare meat options. Basically, because cows are so much bigger than chickens, eating amount of meat would require the death/suffering of far fewer cows than chickens. This should probably be a much stronger factor in my decision-making than my assumption that chickens may be a bit less capable of suffering, especially since I don't have a particularly good reason for believing that.