We've stayed at the Swan 5 times and at the Dolphin once...soon to be twice
I have to admit I like the Dolphin just a bit better than the Swan. It took a lot of convincing from a "friend" (he he he) to try the Dolphin because I was convinced I'd like the Swan better. The Swan is smaller and a little more intimate which is nice and why I liked it and wouldn't try the Dolphin.
When we finally stayed at the Dolphin we realized how (even more) convenient everything was. Tubbi's was just an elevator ride away. The pool was a short walk away (both pools that is)...the sunrise from our balcony on the first morning was breath-taking.
But, I have to admit the best view we've EVER had at any hotel we've EVER stayed at on Disney property was at the Swan when we stayed at a studio room in the main part of the hotel. We had a panaromic view of the BW, EPCOT (including the Illuminations fireworks) and even off in the distance we could see the MK fireworks and the CR on the horizon, it was just amazing!
Both resorts have great CMs and great service. I like Gulliver's the best of all of the full service restaurants which is located at the Swan (but it is just a short walk from the Dolphin).
If you like "liveliness" then you'd like the Dolphin more, if you like "intimacy" then the Swan is more for you. The other difference is that the Swan has 2 queen beds vs the 2 doubles the Dolphin has. And, the Swan has 2 sinks vs 1 sink and a vanity area at the Dolphin. Didn't really matter much to us, the double beds makes for more room in the room, the vanity made for more room for our stuff

You should be comfortable at either

ENJOY!