I like both of them for different reasons. I like the location of 1500. Very centrally located, small loop, so no one site is too far away from the comfort station. Equal distance between both Outpost and Settlement to main bus stops. The only problem I have with 1500 is that the sand area is smaller on those sites and for tent campers that can be a problem. I can't use 1506 at all.
Loop 2000 is newer and is designed for tent campers. All sand pads are larger and have a little "jut out" where the grill is located so that doesn't use space in your main tent area. I can always set up my tents and flys exactly the way I want them. However, Loop 2000 is huge, and it is more likely than not, that you are a distance from a comfort station. It is also out in the boonies. To get to Settlement by sidewalk is an extremely out of the way process.
So that's my feeling on the two loops. I guess I favor Loop 1500 if I can get a large enough site.