I've stayed in both Loops and I like them both for different reasons.
Pros of 1500:
As everyone says, Loop 1500 is close to the pool, the Meadows trading post the campfire program, Bike Barn, and is about equal distance from the Settlement Area with Trails End, Hoop De Doo, Marina and from the Outpost Area. It is also easy to get to either end of the campground from 1500 by way of sidewalks (if you have your bicycle). 1500 is a smaller loop with one comfort station, so any site is not too far from the comfort station.
Cons of 1500:
Small loop, so harder to get per request
Older loop, so sites are a bit smaller. Some sites may be a bit small for tent campers with lots of people and multiple tents.
The grill and/or a tree may be in an awkward spot for setting stuff up.
Pros of 2000:
This loop is newer, so the sites are a little better configured for tent camping.
Each site has an extra "square" of sand where the grill is located so it gets it out of the way of your gear.
The sand pads are larger than Loop 1500 so more room to set up in the exact configuration you desire.
It is isolated and very quiet.
No trees in inconvenient places (There are trees all around, but there are no trees "in" the sites like 1500)
Cons of 2000:
It is isolated.
It is a "long" convoluted way by sidewalks to get to the Settlement Area.
(There is a quick shortcut, but means going down a cast member only road)
It is a large loop with two comfort stations.
There is a possibility that you are a long distance from a comfort station.
It takes two buses to get to the campfire program (unless you walk).
Carol