Honestly, I wouldn't book it. I recently flew first to NRT in Lufthansa First Class and returned on United Global First. The seat itself was fine but the difference in service was extremely disappointing. The F cabin service was almost non-existent at times and while the food was an improvement over previous First class offerings, it was pretty bad. Plus, what I hate is how
inconsistent their service is. I highly suggest you use those miles on just about any award partner.
Two pics from my flight there and back, I'll let you decide what one is LH and what one is United Global First.
