Hey Plutolover,
I don't know of any specific links off-hand...but the basic difference is that the preferred sites are closer to the Settlement (Pioneer Hall, River Country, Petting Zoo...) bus depot and boat dock. They also have a few more perks like cable hookups.
We've stayed in both types of sites. Personally, I "prefer" the preferred. The time saved by not having to wait for a bus to get to/from the Settlement transportation area is definitely worth the price difference in my mind. When you're ending a long day in the parks, it's nice to be right there at the front so you don't have to make a major hike or wait for a Chip or Dale to take you to your loop.
Having said that...I really don't see a quality difference in the sites at all. The comfort stations were always very nice and clean and exactly the same in all of the loops we've stayed in.
Hope this little bit of info helps!
