Grande Vista is Marriot's Flagship resort in Florida... All of the 'Grande" resorts are their top of the line offerings.
Horizons is more cookie cutter... but don't get me wrong, a very nice resort that is designed and priced to be affordable to a larger market segment.
You can't go wrong with Grande Vista... they are just completing their final phase of development. Yes, they are about 10-15 minutes from Disney, but minutes from Sea World.
We've been very happy with our 3BR at Grande Vista, and the flexibility it gives in trading. That said, we are considering selling it... but only because we have bought in St. Thomas and can't find the time to use all the weeks that are building up on the books.
Rich