Interesting question. A couple of airports I've flown from recently (LAX & JFK come to mind) have offered both SkyPriority and PreCheck lines. I've tried both but my experience is a bit limited. At LAX I used SP but could follow the usual pre-check criteria of keeping my shoes on and laptop in the bag by showing the person manning the belt my boarding pass again. In JFK I opted to just go to the PreCheck line.