As someone who hasn't ridden Guardians but has ridden Tron, it sounds like, from reviews, that Epcot finally has a "knock your socks off" headliner attraction, but I can assure you, Tron won't deliver that when it comes to Magic Kingdom, and that's a shame.
Each park has a modern headliner (from my point of view)
- Flight of Passage (Animal Kingdom)
- Rise of the Resistance (Hollywood Studios)
- Guardians of the Galaxy: Cosmic Rewind (Epcot)
But Magic Kingdom doesn't. I realize Magic Kingdom doesn't need more draws, but I feel that each Disney park around the world needs one showstopper attraction that makes people think "wow, that alone made this whole trip worth it."
Tron is a solid ride, but far from a headliner. Would I take it over, Everest? Probably not.