Contemporary standard rooms are ~400 square feet. Poly is about 415, and Grand Flo is biggest at 440. That said, for a group of 4, all are spacious, and I'd go with the theme/cost that best speaks to you. Contemporary Garden Wing is typically the least costly option amongst the room choices at these three resorts, unless you hook up with some deal$.
Most Wilderness Lodge rooms are in the 340-350 space unless you upgrade to the "Deluxe" room, which costs more.