The choice between the Swan or Dolphin really depends on what you want---quiet and more intimate, but with few "inexpensive" places to eat and fewer amenities (i.e.--laundry in the building) or bigger, busier, more festive and, some say, more convenient , with the less expensive restaraunts and the laundry(Dolphin).
They share buses to and from the parks and each has it's own bus stop in front of the respective hotel. They share the boat dock for the MGM/Epcot Friendships, so, transportation is not a consideration.
Both offer king size standard rooms. The Dolphin, being the larger resort, has more rooms with views, but, also has more rooms with less than desirable views.
While parts of the Dolphin are closer to the Grotto pool than the Swan rooms, there are also some Dolphin rooms that are farther away from the Grotto than some Swan rooms.
Hope this helps....or. at least hope that it didn't muddy the water even more for you!