I think it can be important to keep in mind that it isn't as if any of the resorts has its own fleet of buses under its own control. The buses are dispatched from a central point, and the bus service is going to be whatever it is, no matter what resort you stay at. No resort consistently has better or worse bus service than any other, since no resort has any control over the dispatching of the buses. If the parks are very crowded at a busy time, then the buses will be more crowded no matter where you're going. A more important consideration would be things like how many internal bus stops are at your resort and where your bus stop is on the circuit - will you get picked up first in the morning, almost guaranteeing you a seat, or will you get picked up last, risking a full bus.