I personally draw the line at ability to be in pain/suffering, rather than self-awareness. And so trying to minimise the suffering I cause to other beings, within practical limits - living in a capitalist society, everything I buy or use was at least partially made available by human exploitation.

But back to animals, I do agree that, say, a prawn is most likely capable of less suffering, than say, a cow or chicken, since their nervous system and "psychology" (if a prawn even has such) is much simpler. So if someone was truly forced to eat animal protein for health reasons (with the assumption that human health is of elevated priority over animal suffering), then I do think that eating animals of lower ability for suffering is more ethical than those with higher. Both prawns and cows can feel bodily pain, but animals with higher cognitive abilities are probably also harmed by all the ways in which factory farming stops them from being able to express their natural behaviours.

I am of mixed attitudes towards treating animals and humans on the same priority scale. My emotional affection to people I know and my awareness of societal norms tend to make me shy away from saying that a fetus/newborn or a person with profound intellectual disability are potentially less capable of non-pain suffering than a cow or a dog, but intellectually it would only be consistent reasoning. (Same with drawing parallels between human slavery and animal captivity and exploitation.)