I ran across this interesting quote in Barrett's classic commentary, The Gospel According to John, on John's style:
John can hardly be said to create a new vocabulary, yet his choice of words is undoubtedly distinctive. His Greek moves slowly and within narrow limits, which clearly distinguish it from the other gospels; but it must be acknowledged to be an adequate instrument for the author's purpose. In spite of the small vocabulary the reader never receives the impression of an ill-equipped writer at a loss for the right word; rather that of a teacher who is confident that his message can be summed up in a few fundamental propositions which he has learnt to express with studied economy of diction (7; Second Edition).