Good question.  I enjoy both.  Most people (including myself) who start to Wing get a bit obsessed with learning it and do nothing else for a while.  Then you settle down and get back to kiting.   I kite when I cannot wing....meaning light days (9-12 MPH avg) or when the waves are too big for my wing skill level, but my preference is the wing whenever I can.  I also kite when it has been a long time and I am concerned about losing my kitefoiling skills.