We stayed at the Dolphin in May and had heard the bus dropoff at the TTC wasn't the greatest. We did that a couple of times and it was kind of a pain to get on a boat or ride the monorail rather than just getting dropped off and walking up to the park entrance (and to be honest, the bus dropoff for Animal Kingdom seemed farther and more arbitrary from the Swan/Dolphin bus as well). Walking to the Boardwalk, as Carolyn mentioned, to catch their bus was the best option, and is the same distance from both (maybe slightly closer to Swan, but not enough to make or break a decision). We did ride the bus to/from the Yacht Club once but preferred the Boardwalk.
Are you renting a car? I had seen others mention that if you rent a car and drive to the park you can park for free if you stay at a Disney resort, and I think the Swan/Dolphin qualify. I probably would go that route if I did it all over again just to get to MK and AK.
I haven't stayed at the Swan, but when choosing between the two the different in-hotel dining options caused us to choose the Dolphin because it seemed slightly more kid friendly. The ice cream shop on the first level is worth the price of admission, and the restaurant around the corner has plenty of kid-friendly food options.
We loved the location of the Dolphin as we love to walk to the parks (Epcot/Hollywood Studios).