Flew ZRH - LAX - MUC recently in LX F und LH F and if you have a choice, definitely book LX F. The F seats on LX are much better: you have a really comfortable seat, you have your own suite with a door, the bed is very comfortable to sleep in. On the other hand, I found LH F rather less comfortable for sleeping, as I also had the feeling that the seat was not completely flat - but maybe it was just defective. I found F&B and the service on LX far better than on LH, although we may just have been unlucky with the crew here.