Both are great rides and either one is worthy of a win in this poll really. AS others said they are very different rides so it's hard to truly compare. I love them both for different reasons.
ToT is great thrill, love the atmosphere of it. The Twilight Zone pre-show is fun, and the queue through the gardens with the hotel looming, and the lobby/library space is great.
Gringott's has the amazing queue (especially the bank lobby), fun coaster/dark ride expereince with lots of fun elements like the tilt track and launch. I do feel it tells a more complete story and feels more immersive than the elevator drop tower experience. So I do give a slight edge to Gringotts but would hate to actually have to choose between them in real life.