I’ve stayed at both.
I would lean towards Dolphin, and the only reason would be because I know which bank of rooms to stay in to be closest to the pool complex.
If I had no interest in pools, I would choose Swan.
We go to the pools every day, sometimes twice per day. We stay in the Dolphin rooms with the patios that face the Swan pond specifically because it’s just steps to the pool, and also there is a walkway to the bus stop.
The pros for Swan, in my eyes, were the better bathrooms, and the shared Disney Bus picked and dropped off at Swan first, and the hotel was smaller.
For us, the pool is the more important deciding point. GRANTED, if you get a room at Dolphin that is far away from the pools, then you might have to walk just as far, or maybe further than a Swan room. I just know that staying at Swan, after 3 days or so, if you’re going to the pool complex AND touring parks all day - the steps to the pool complex start weighing on you. It’s not a FAR walk, but when you add in all of the other walking? Going to the pool complex started to get old pretty quick. We found the perfect Dolphin rooms for us: King room with sofabed, right next to the pools. We’d never take the double beds.
If we weren’t such pool people, for the same price, we’d pick Swan all day, though.
P.S. if you like sushi, make it a point to try Kimonos. Also, make it a point to try sub sandwiches at either of the grab n go spots. These are all hidden gems (many people would say that all of the restaurants at Swolphin are hidden gems - hopefully they’ll all be open when you go.)