I've stayed at both the Swan and Dolphin, and loved it!
The Swan I love because it's a bit smaller, the room felt cleaner and fresher. The Dolphin was still wonderful. When it's been just myself and the kids, we did a king bed and a sofa sleeper once, then once the room was too small for the sofa sleeper to open, so I had them take it out (yes they will do that if you tell them to) and bring in a rollaway bed instead. My DD and I can share a king bed, then my DS took the rollaway. When my DH was along on one trip, we got connecting rooms with one king and two doubles.
The service is good - we got room service a few times when we were tired from being out all day. It was always decent, and they had a kids' menu so the kids could get something appropriate for their appetites. I also went down to Kimono's a couple of times and carried out sushi - my son loves it (he is an expensive date).
The TV choices are much better than Disney resorts! They have movies on demand, which is nice after a long day (and you can watch it for 24 hours, so while getting ready in the morning replay it for the kids!). I wish Disney had that. It was nice to order food and let the kids pick a movie at the end of the day!
The location is the best at Disney, hands down. We go to Epcot almost every day or night, so walking there is great.
The pool area is very nice too, and the laundry room is right nearby. I'll do a pool/laundry afternoon every couple of days.
If it were a choice between any Disney resort versus the Swan or Dolphin, I would pick the Swan or Dolphin any day.