Agree with others, UA for the seat, LH for the catering. I did an LH flight last month (A350, my first long-haul with them in a while) and honestly didn't think the seat was that bad. My only real complaint was that it was obviously worn out - tray kept getting jammed, remote was touchy, etc. Admittedly it was a daytime flight and I was in the middle pair of seats. The food wasn't amazing even but the presentation was far better with a proper menu that included a wine list, seperate courses, etc. Not to mention that you get a full serving.

I'm doing my next two EU-US flights on United, but only because there weren't any good LH flight options - I'm not taking a risky 1-hour connection in FRA just for a somewhat better flight experience.