In normal times, I think I'd do LH F. Just for the FCT, bigger and more private seat. Also, the B777 is a very noisy plane these days.
However, a lot would depend on how "normal" LH is. There was a recent trip rep
SFO777 that said the FCT was closed, and the whole FRA experience was pretty awful. The LH F service was also a bit "iffy".
If it was an EK A380, that would change my mind...