Its all very subjective and the place is very spread out. My personal favorite is the 1700 loop. Its the least expensive of the full hook up loops (water, sewer and electric) and my favorite of the 4 loops in that price category (loop 1600-1900). We were in 1710 last time and it was very big and had the sand pad behind it where our oldest son and his girlfriend set up their tent. that way we had all 6 of us on one site and we werent all crowded into our camper plus they had their own space. We take our golf cart because its so spread out, you do not want to rent from Disney since they are up to 60 per day for theirs. Many people I know rent from Kennys since he delivers and is much cheaper and offers great service.
The dog park is a lot of fun and about 3/8 mile from that loop. Our dog goes nuts for the park, just mention the dog park and she is on the golf cart ready to go.
If you want to be closer to the marina and Pioneer hall the preffered loops would be for you (loop 100-500)
If you want a little bigger (it varies since some arent any larger than the 1700 loop sites) look at the "premium" sites which would be 600-1400
My money is on the 1700 loop, the first 25 sites or so are pretty wide and have a good bit of room between them, there is a canopy of pines in that area also, the odd number sites back up to one of the internal roads and the even back up to a common area in the middle of the loop.
You can request a certain loop when making reservations but they dont guarantee anything.
If you want to read advice from a hrad core group of people that go to the fort, google "fort fiends" and go to that site, you will see me there also.
Scott