To me, the interesting thing about Suki is that she is such an understated character; she doesn't have any disproportionately pronounced traits like Aang's flightyness, Ty Lee's ditziness, or Iroh's love of tea. She is just a person who, for the most part, doesn't get big "This is who this character is" moments the way the others do, so she ends up being much more balanced and subtle in her characterization, if not quite as fun and outrageous as the others.