I sent an email to Ancestry about six months ago asking the same question. I was told that the items on each site were still separate entities. This was a big disappointment, as I am an Ancestry World Member and do not see spending ANOTHER fee for a site that is owned by the same company. I do know that I had found some data on genealogy.com long ago that has not been found anywhere else online.
As far as a personal preference, familysearch.org is the best free info site out there by far.