In my experience several companies prefer flap 30 to flap 40, however, if you like to operate the aircraft efficiently, & are capable of flying CDA's, you won't be aiming to be stable before 1000' IMC or 500' VMC so really no big deal in fuel burn between 30 & 40 is there ?
I always found the 800 much more speed stable on the approach & much less critical in the flare with flap 40. They always said to me, in strong crosswind better 30, in response I would say I have seen more flare /balloon/ float /flop& probably drift too
landings with 30 , so I always prefered 40 no matter the wind. The 800 is fast enough thanks with 40, when I am in the back please contemplate using all that Boeing provided
