Going from central Budapest to Vienna airport on a Friday in October for a late afternoon flight. Found train service from Keleti that takes about 3 and 1/4 hours with 1 transfer in Vienna. Then there are two direct bus services: Flixbus from Nepliget and Regiojet from Kelenfold. Buses are about half the price of the train and less total scheduled time. I'm figuring its down to the buses because it avoids a transfer (however easy) and cost. We'll be allowing plenty of time in the event of traffic the bus might run into as opposed to the train.
Any thoughts on the differences between the two bus lines from the standpoint of reliability, comfort, convenience?