I've stayed at both, and I would choose the Dolphin without question.
The Dolphin is a deluxe resort while CSR is a moderate, and this is evident in many ways. The rooms at the Dolphin (especially the beds) are much nicer, and we've never heard any noise from neighbors at either the Swan or the Dolphin, but we could hear every sound our neighbors made at CSR.
Another major factor is location. You just can't beat the location of the Dolphin. CSR is also much more spread out, and you have to take buses to all the parks. At the Dolphin you can either walk or take a boat to Epcot and MGM. Plus, the Dolphin is right beside the Boardwalk area and Fantasia Gardens mini golf, offering you many additional entertainment options.
The restaurant selections are also much better at the Dolphin. Not only do you have the great restaurants in the Dolphin and the Swan right next door, you also have all the Boardwalk, as well as Yacht and Beach Club, restaurants next door.
Both resorts have great pools, but we actually prefer the grotto pool at the Dolphin, and it is much less noisy and crowded than the dig site pool at CSR.