I wouldn't sweat the transportation. On any given day, transportation can be good/bad/indifferent at any resort. When you are on-property you are a guest, and they will make it better. Somedays you'll wait for a bus 15 minutes, sometimes not at all, it doesn't matter. Always allow travel time into your plans. Don't leave your room and expect to be entering a park in 5 minutes. We always allow 30 to 45 minutes to arrive at the park gate from the bus stop. Coming back from the parks can be a little slower. Still you are not going to get better. Lets look at some real-world times:
To Magic Kingdom Gate, from AS.
Car: Walk to Car. (5 mins) Drive Car (15 mins). Park Car (5 mins) Get Parking Lot Tram (5 mins). Ride Parking Lot Tram (5 mins) Walk to gate (5 mins) - total 40 mins.
Bus - Best Case: Walk to bus stop (5 mins). Wait for Bus (5 mins). Ride Bus (15 mins) Walk to gate (5 mins) - total 30 mins.
Bus - Worst Case: Walk to bus stop (20 mins). Wait for Bus (5 mins). Ride Bus (15 mins) Walk to gate (5 mins) - total 45 mins.
Even at its worst, the bus isn't bad. Buses are re-assignable. That is, if there is a shortage, or too many people in one spot, they put more busses on the situation. If a bus is full and people are waiting, the driver radios ahead and they send another. Again, the value of staying on property is they take care of you, every step of the way, from the rides, to your bed, you are a guest of the same resort.