I got a quote from
Dreams Unlimited, and it was actually a little higher than going direct. I could be wrong, but I think they only have access to a block of rooms for each resort to book. So by calling WDW direct, you might be able to get a better room or view or size room, and by going through DU they might be out of that type of room. I'm not sure that is actually how it works, but that is how someone explained it to me.