The real, new Polaris seats are better than the Lufthansa J seats. However, I don't think that any of the United 787-9 has the new Polaris seats. The old 787 seats are inferior.
I get that you don't care about food or alcohol, but service goes beyond that. On Lufthansa, you will be treated like a human being and a valued customer. On United, the odds are about 2 to 1 that you will not.
p.s. I don't want to be a grammar scold, but it hurts me when you form plurals with apostrophes. ;-)