Having done numerous CW and F flights in the past few months, some paid, some redemption and some with the recent buy full fare CW fly F o/w promo, there is clearly a difference between the two products in terms of amenities, food, priority etc, but the one thing I have really noticed, and the only thing that to my mind justifies taking F over CW (whether paying miles or money, and assuming limited resources/miles), is the calm and quiet ambiance in the cabin. CW is great, but does feel a bit like a flying dormitory, whereas F is just way more serene and you really feel like you have your own personal space. Of course, the one partial exception to this is the UD on the 747, which is essentially F lite from an ambiance perspective.