If you have a connection in a UA hub (except for DEN) then the Polaris lounge is your friend and will beat LH soft product out of the water. Agree with the others...the Polaris seat is the better seat but the onboard service (soft product) from LH will beat UA. LH already announced their new Allegris business product doesn't start flying until later in 2024 although it's possible some newly delivered aircraft may have the new seats. Apparently supply chain issues...
If you give us specific routes we can help you with the options. But it sounds like you're looking ex-FRA or ex-MUC. UA flies a 764 out of MUC but not out of FRA.
-RM