The first case, most would say, is “creepier,” while the invasiveness and pain is clearer in the latter.
Facebook has decided that the best way to increase revenue is to be creepier.
I couldnt feel any creepier if it were the Black List that was going to be read.
What he saw was creepier than creepy, and surpassed all he had ever dreamt of.
1794, "characterized by creeping," from creep + -y (2). Meaning "having a creeping feeling in the flesh" is from 1831; that of producing such a feeling, the main modern sense, is from 1858. Creepy-crawly is from 1858.