I think Disney's "trump card" is and always will be the value of the Disney brand itself. People go to Disney for DISNEY, with any individual land or attraction having relatively minimal impact under that umbrella. People who enjoy Universal as a theme park aren't going because they have any great love for the "Universal Studios" brand, because "Universal Studios" isn't much of a brand at all. That's why Universal sees attraction-driven spikes from brands they import like Potter and Transformers. As much as people complain about DHS as "Disney's Unrelated IP Park," Universal Studios is built on that very concept.
Off topic: Do the Universal parks have an overarching "story" at all? Or do they freely acknowledge that they're a bunch of unrelated properties clumped together in a theme park. When you visit WWoHP, are you actually visiting that "world," or visiting the "movie world"? How is WWoHP in Islands of Adventure reconciled against WWoHP in US?