I have flown AC NH and SQ economy in the past few months and SQ was great for service, an amenity kit in E, wow, and the seat was good as I checked in early at the airport and got an emergency row with unlimited legroom. NH was also good I left decent space and service was great.
AC is actually not too bad too but again depends on aircraft, their 77W 10 across is just as brutal as UA 77W 10 across. I have not flown AC 787's yet but I have survived UA 789 service to / from SIN many times and it really was not too bad.
I think another factor you should consider is the loads, if you can get an empty seat beside you in E+ on UA, I would say that is your best bet. I have had this several times to / from Asia due to E+ costing a ton for non-elites, and it makes it a really pleasant flight.