I think it's more personal preference as opposed to advantages/disadvantages. Sure the layout of the J cabins are different but the service etc remain the same. I would suggest if travelling alone then the Airbus config would suit (specifically 2K-6K) due to the 'private' feel created by the partition, but that's just my personal opinion Beware though, if travelling after 1830 from the east coast US you will be on a GNF and upstairs on the 747-400 is allocated the snooze zone as is rows 1-7 on the Airbus.