The accessible option - Dublin Bus 747-757
This review is especially helpful for those who have or use the following: Wheelchair
This is the turn up and go airport bus you can actually bring a wheelchair on. Their competitors require advance booking. Ride is a bit bumpy as it's a standard city bus not a coach but they use the port tunnel so the trip to the airport is half an hour from the city centre. There's a cheaper but slower city bus (16) as well.