If you can bag an NZ seat then that's always my first option to/from LAX, you can't go wrong with it.

AC' s new C suite is pretty similar to NZ and Virgin, just a cheaper version but still totally flat and very comfortable, just lacking the quilt, a bit of extra width and extra padding of NZ but to its credit I always sleep like a log on both.

AC is always my first option when travelling back from ORD, I'd transit thru Toronto or Ottowa to LHR rather than use UA direct to LHR from ORD. I love the AC service, the crew are generally much more amiable than UA and even rival some NZ crew plus in their lounges you don't have to buy drinks at the bar, as opposed to UA where you do (plus they have Guiness on tap). I've also travelled on them from Vancouver and Calgary on the 763 services which are great. Just avoid the 330's as they (to the best of my knowledge) are still the old C configuration.

One thing to consider about NZ and AC (and Virgin) is if your travelling alone the herrfingbone layouts are very private but if your with the one you love (or care for a bit) they are not a great enducer of conversation so please bear that in mind.

OK I'm going to be contravertial here but LHR is NOT that bad. I know that may not be the popular opinion but IMHO it's true. I transfer thru LHR from T1 to T1, T2 and T3 just about every week with BD, LH, SAS, TP and AC and rarely experience any issues. You just have to be prepared not to buy duty free liquor in transit as you won't get it thru security.

I personally don't like LH or LX C class on a TATL night flight, especially when compared to AC. However the service on LX & LH in first is fab.

I've only heard terrible reports from colleagues about the longhaul TP service (rates as highly as US) so I wouldn't even think about it if I were you! The short hop from LHR on TP is very bearable though so don't be put off LHR because of the TP connection to LIS, they are plentyful and a only about 2 hours long.

Have a great trip.