Bus - Emirates Express coaches are fast, cheap, free wi-fi, reclining seats but limited collection/stopping points. It is an express service.
Taxi - no comment.
Fly - I think there is a scheduled service from Basateen Executive airport in Abu Dhabi but maybe it goes to SHJ not DXB?
Helicopter - recent press reports about a whirlybird equivalent of Uber !!
EK or EY will both do courtesy coaches if you have an onward flight ticket.