My two cents from my experiences:
- ZRH is a much more convenient airport to connect than FRA. They drive you to the plane from some lounges in FRA, but the total walking usually is still more in FRA than ZRH
- The A380 is a much, much nicer plane than the 777 (noisy, dry air, air pressure)
- Seats on LH and the new 777/330 seats are good for sleeping. LX 777 has a bigger screen
- Food: LH has caviar, otherwise it can be hit and miss and personal taste. But you will not be hungy on any of them
- Service: mostly excellent on ZRH and MUC flights, hit and miss on FRA
There is no clear winner for me. I would pick based on schedule (On westbound flights I would pick a later flight because I can then sleep better) and price.