Welcome to the Disney Parks Moms Panel Lindsay ~
Those are excellent questions! I am actually at
Disney's Grand Floridian Resort & Spa as I am answering your questions.
In my opinion, like you said, it is a proximity thing. The main building provides a little quicker access to the monorail. Shopping, most of the dining locations, Mizner's Lounge, and Ivy Trellis Salon are located in the main building. However, some of the outer buildings provide quicker access to other things. For example, Sugarloaf, Sago Cay, and Conch Key are closer to the marina. Sugarloaf and Sago Cay are closer to Gasparilla Island Grill. Conch Key and Boca Chica are closer to Narcoossee's. Conch Key is the closest building to the dock where boat transportation is provided to the Magic Kingdom park. The main building and Big Pine Key are closer to the Beach Pool, while Big Pine Key and Boca Chica are closest to the courtyard pool. If you want to see the fireworks at the Magic Kingdom from your room, you will want to request a Magic Kingdom view in Sago Cay, Conch Key or Boca Chica.
Now having said all of this, all of the outer buildings are really not that far from the Main Building. Disney's Grand Floridian Resort & Spa is not as spread out as some of the other larger deluxe resorts like Disney's Old Key West Resort or Disney's Saratoga Springs Resort & Spa.
I think the rooms in the outer buildings are nice. I love the room I'm in. For me personally, I'd go for an outer building and save a little money.
Please feel free to visit us again with all of your planning questions. We are hEAR for you!
Wishing you minnie magical memories :-) Allison V.