Strictly from a quality-of-view standpoint, Contemporary. It is closer and less obstructed. It includes a sweeping vista of the parking lots below as a bonus, but at night when Tomorrowland and the castle are lit up, it's lovely.
But I prefer the Polynesian resort in general, and while there are often tree-covered islands between your balcony and the theme park you are viewing, when Wishes is going off it hardly matters.