Hiya Marni!
My family has stayed at both the Swan and Dolphin numerous times and we enjoy both.
We prefer the Dolphin only because we like eating breakfast on the lower level there, so it is a shorter trip...so, yeah, I just admitted we are totally lazy! But really, that's the only difference for us. Oh, and my kids like the Dolphin fountain more!
But in terms of the rooms, staff and cleanliness? They are very similar. I own a small hotel myself and I'm very picky so I look at weird things when I go into a room. I don't have any complaints with these rooms.
Both hotels are a great location from Epcot, Hollywood Studios and The Boardwalk! Taking the boat to Epcot and Hollywood Studios is one of my kid's absolute favorite things.
I recommend them...and that is a great price! I hope that y'all have a great time!