In the areas where I have traveled so far with the coach, Flying J generally have RV islands whereas Pilot does not. The islands have not so far been hard to get into or out of in my experience. The $.08 discount I get as a GS Life Member usually brings my price below other stations in the area I'm fueling. I also can not see driving out of my way to save another penny on diesel.
It is generally fairly easy to find a PFJ station on your routes. There is also a smart phone app I use from Pilot, and
a special POI file for MS Streets and Trips that lists all PFJ stations along with MANY other things.