They both have their pluses and minuses. As always, it depends what the OP values. LH has superior food, wine and service for sure. But, LH gives you a choice of soup or salad. On UA, those are two different and included courses. LH desserts can be "creative" but also boring (Friday was a piece of chocolate mousse cake--yawn) but UA has the sundaes. On the other hand, for me (don't know about the OP), I'll trade the caviar service for a sundae any day!

UA's new suites are more private and wider than LH's standard/older seats. Both provide nice blankets and pillows, although two pillows with UA and one with LH. My biggest LH complaint/UA praise is cabin temperature. Without exception, to me, LH cabins are too hot and make sleeping difficult, and their aircraft have no fresh air nozzles. UA cabins are fine but all seats have fresh air nozzles and in FC have two if not three per seat.

If sleep is important, the wider UA seat with the more comfortable cabin wins with no doubt. If food and wine and service are important for the flight, then hands down to LH.