You are in for a treat! LH F is worth the incremental 20K miles over US Envoy, easily. Also, LH F is on the upper deck on the 747, which beats the nose location on other airlines hands down.

I don't know if you've flown intra-European routes, but C class there is no more than glorified Y. The flights are short, though, so you should be OK. Enjoy and Guten Flug!