As that well known expression goes - "up to you" as to bus, taxi, limo, etc. - If you do choose Bell service, if I recall correctly, you must now advance book your trip online with them - no pick up at airport if no reservation.

The Airport Bus opposite Pan Pan is convenient for going to the airport - but, you can be delayed if coming from the airport. I took it to the airport and then the train into Bangkok. On return, I went directly to the bus desk and was informed the next bus was full and I would have to wait 2 hours for the next one -- however, they did provide another bus, so the wait was only an hour.