This is very close, but I think at this point in my life, I have to say Epcot actually may edge out MK slightly. They are very different types of magic, but I remember both parks as a child giving me that exciting hope of something just out of reach... what i call magic. Now, a few places in MK have that, but it seems to be a bit more vicarious. I am enjoying seeing the magic in the faces of other guests (usually younger), not my own. However, I still get that feeling in a lot of Epcot, especially in World Showcase at night. I will say that music is a HUGE part of the magic for me, and the rich, orchestral scores of Epcot just do more than the jolly, simple tunes of MK. I will say a lot of Epcot's magic has left, as has MK's.
Tough call, though, on least magic. I would say MGM might have it simply because the story is a bit more contrived. The "working studio" theme never did much for me, and now the attractions don't have quite enough story to be the foundations of "Disney magic" like Pirate, Spaceship Earth, American Adventure, or Space Mountain can (don't get me wrong. ToT, Muppets, and RnRC are OUTSTANDING. They just don't create that feeling as much). I also must admit that Fantasmic! does nothing for me at all. (runs for cover)