First, I would like to thank the OP for asking this question as I have been meaning to ask the same but my AONE isn't for another 16 months so I was waiting a bit. I will bookmark this and check again in about 14 months when I prepare to purchase my ticket to see if any changes have occurred.

With that said I wanted to ask opinions from those in this forum with mainly 3 factors in mind. I also woud like to ask the same question about SYD-LHR service. The 3 factors I am primarily interested in are sleep comfort, food quality and service of which a nice perspective was already provided by Zeffer. Oh and please remove alcohol and caviar as factors of consideration in my case as I don't drink and find caviar overrated. I have a lot of friends who both drink and love caviar, but they aren't traveling with me.

Actually in my case I will be traveling both BKK-SYD and SYD-LHR and will choose BA on one segment and QF on the other so I can experience both F products. I will be connecting in both cases, on the BKK-SYD to a QF connection, and on the SYD-LHR to a BA connection. Lounges available, lounge services provided, and ease of making the connection are other factors that need to be taken into account in my choices, so if there are major differences there then please let me know. Other than flying AA to LHR I am unfamiliar with BA or QF transits at LHR. I have never been to SYD so all that is new to me. Thanks in advance for any and all feedback.