For an overnight flight, in general would go UA over LX. I find the LX seat - especially if not on 77W - fairly uncomfortable for sleeping and their bedding is terrible. Food and wine though is much better on LX, so would preference an LX option westbound.

Lounge-wise, it’s a bit of a toss-up to me between Polaris Lounge and LX ZRH SEN lounge. As an American, I find the LX lounges a bit more “fun” in that they feel European but net net the food (from restaurant, not buffet), wine and drinks are probably a bit better in Polaris lounge. I like both in any case