I ran parallel tracking for a year before getting autotrac on a 4710.  I really don't have anything good to say about parallel tracking.  You'd be better off going with foam instead of PT.  With PT you don't have a frame of reference ahead to see what way to drive.  I spent all my time overcorrecting one way and then the other and couldn't take my eyes off the screen for very long.  That doesn't work when you're trying to watch/control the boom and move quickly.  Autotrac is the cats meow on that rig, takes hours off the day.  You don't get fatigue trying to follow foam or indicators and you can watch the boom or feather boom sections accurately.  I don't have any experience with EZsteer, but I'd buy it before going with parallel tracking or lightbar.