I find it interesting that these aliens are at the same time "superior" and "inferior" to humans, so the better word would be... different.
"They" have abilities that far surpass what we can do, but their form is "fragile", and "their" comprehension of emotion is really low which creates errors in "their" evaluations.
Sure "they" succeed with most people, but that is because of other factors too that help maximize the psychological attack, but to someone like Deido and others that have a strong and solid sense of self, "their" attacks don't work.
I would say that it is because of the "solidity" of our bodies, as "they" are fluid beings our "cage" like body affects the mind in ways "they" don't completely understand.