If you are Avios rich and both classes are available?

In that situation I do choose F over CW, but I'm usually using an Amex 2-4-1 so to me the Avios premium is not that great. If I only had enough Avios for F in one direction I would always choose the day flight and preferably one originating at LHR. Saying that, my next reward flights are LGW-UVF-LGW in F, so no LHR and one night flight.