One other thing to think about (maybe others can provide more info) is what type of buses are most commonly used with each resort.
We had stayed at many resorts traveling with a w/c and only rarely encountered buses with stairs and lifts (rather than ramps). But, on our last trip we were staying at SSR with my DFIL who was using a
scooter and only 1 of the buses we took all week had a ramp!
The lifts seem to require both more skilled scooter drivers and more skilled bus drivers. In his first couple of days, my DFIL had several inelegant boardings that ended up with someone lifting the scooter somewhere. We had one driver who took about 10 minutes to figure out how to get the lift down. We had several drivers who opened the front doors and started letting people on before checking to see if anyone was waiting to load at the back. (At least, that was the argument made, but, it's confusing to me since they had to drive past him to pull in!) In one case, we'd been the first people at the bus stop, but then there'd been a long wait and 40-50 people wanted the bus by the time it arrived at our resort stop. A half-empty bus pulled up, the driver opened the front door and refused to speak with us until after everyone else had boarded--even though a member of our party was at the front of the regular line. Then, he told us there wasn't any space for the scooter and we'd have to wait.
I don't know whether we had bad luck or whether there's something to the type of bus. As I said, we've never had these problems before, and we always travel with a w/c.
Does anyone know why we were getting the buses with stairs? Are they more common at SSR? (If so, which resorts use them the least? I'd recommend those resorts for the OP.) Are they just becoming more common in the fleet?