Each of these words suggests an attempt to note and analyze characteristic features of some item or person. Differentiate involves pointing out exactly and in detail the differences or partial similarities of two things being considered: "It is difficult to differentiate between the symptoms of pneumonia and influenza." "One who takes up the study of cells must quickly learn to differentiate among them in size and structure." Distinguish has much the same meaning as differentiate but implies general recognition of characteristics that establish the identity of something without giving attention to specific details: "It is easy to distinguish an elephant from a buffalo."
Dictionary of problem words and expressions. Harry Shaw. 1975.