I voted for the Polynesian. When we visited and dined at the Polynesian on our last trip we decided unanimously that we'd stay there on our next family trip. We'll be staying there for the first time in July.
Why I chose the Polynesian: The location, the views, the restaurants on-site, the size of the rooms (2 queen beds plus a day bed means that our two teen boys don't have to share a bed), overall resort theming, volcano pool theming, transportation options (monorail, boat, bus, plus a few steps away from TTC), excellent reviews of the concierge building and lounge, and lastly it has a nostalgia factor for me; I remember seeing the Polynesian as a child. At the time I didn't realize it was a hotel, but I thought it looked amazing anyway. It's one of the two original on-site resorts at Disney World

Ahhh....only 96 more days!
We've stayed at the Grand Floridian before and enjoyed our stay there, and will probably stay there again on a future trip.
As for the Contemporary, I plan on staying in a tower room at some point even for just a night or two, purely to fulfill a childhood wish. LOL Otherwise, the Contemporary holds no appeal to me at all. I wouldn't stay in a garden wing room unless it was the only room left at any of the deluxe resorts.