Tnkrbell,
As everyone else has said, there are only a few differences. We stayed in Sugar Loaf and found it to be very comfortable. I just called the Grand Floridian for you and the Sugar Loaf DOES NOT offer the evening Cordials or Alcohol, they have Twilight Refreshers from 5 - 7 but no late night offering. When we stayed there they didn't offer the evening cordials, but the rest of the offering where Fantastic. We loved them. The atmosphere was like the others have said "more relaxed". The Castmembers where all Super Nice and very friendly. I would do it again in a heartbeat if they had a Castle View, but the Main Building has always been a Dream of mine and one day we will do that but until then I will settle on Lagoon View.
I hope this helps,
Wendi