Hello!
Well, fortunately, during Walt Disney World Marathon weekend, ALL of the Disney resorts are considered host resorts and will have bus transportation to and from all of the race weekend events. So, that won't be an issue, whichever you choose.
Those two resorts are very different. The Art of Animation Resort is brand new and is amazing! It's fun and whimsical and just really unbelievable! The only downside I can think of is that this resort is not within walking distance to any of the Disney parks.
The Swan is also very beautiful and more of an "adult"-style, typical resort. I would say that one of the definite advantages to staying at the Swan would be that you can walk to Epcot, Hollywood Studios, and around the
Disney Boardwalk area.
You will be happy with both choices. It really depends on what you are looking for and if the hotel's theme or its proximity to the parks will be more important to you. Please let me know if you have any other questions!