I believe it's 2 queens, not 2 kings in the standard rooms at the Swan. Also, the Swan rooms have a second sink outside the bathroom itself which is nice if you have a bunch of people getting ready in one room.
The Dolphin houses Tubbi's (24 hour buffeteria) and a laundry and gameroom, the Dolphin's west end is a little shorter walk to the Grotto Pool (which is shared by the two hotels).....so for those reasons sometimes pople with kids prefer the Dolphin over the Swan. It's only a couple of minutes walk between the two though.