Park by size. If you need the extra length or space, take it- that is why they are there.
An RV'er with his family along has every bit as much importance to be rested on the road as a truck driver- no matter what regulations may or may not apply.
Personally, I believe the more important issue is for RV'ers to be cognizant of the "order" of things, recognizing and respecting the flow in and out of the areas. Leaving lots of room for entering and exiting drivers, not parking on corners, etc.
Those who claim 'exclusive access' to given parking areas or facilities are not giving the same level of consideration they are expecting from others.
If you need to rest, rest. If you need to park, park. As for truck stops' benefit? It's far more likely for a family of 4 or more to be more financially beneficial than one driver in a truck.
Don't get me wrong. I have family and friends who drive truck and understand that point of view quite well. Truckers I know value their family above all else- that's WHY they are away from their families for extended periods to provide for them.
Professional drivers ABSOLUTELY understand the importance of family and will often bend over backwards to watch out for yours, too. Including being safe and rested on the roads.
Be safe out there and share the roads! :)