I'll believe the upgage when it actually happens, and if you have some data on AA's loads vs. UAs loads, I would be curious to see it. I know no where to find that stuff on a route specific basis. Checking fares, they bounce around (as does how full the plane is) but I see no decernable advantage to UAL. Currently MU (skyteam) flies 1x or 2x 333 as I recall, UAL 1x 788, and AAL 1x 772ER.
AAL has traditionally had very little pacific network, while UAL was the "go to" carrier for West Coast to Asia service, with that edge (and until recently the largest presence at LAX) its surprising that UAL is not doing better.
There are a few basic things you are forgetting. First, EWR-HKG is a polar route exclusively. NYC and HKG are basically opposite each other. Plane flies East to HKG then flies East back to NYC. The plane basically picks up range going both ways. Even then, its at the edge of the 772ER range,and has weight restrictions at times. Flight time at about 16 hours is the max for a 772ER.
SFO (or LAX, another 350 mi longer) to India can't go East then East again,. It has to go West to India. So it looses range going to India. This puts it well outside of the range of a 787-8. I think SFO-India would be more like 17-19 hours.
There is some history here. In 2008-9 Jet airways flew to SFO from BOM, used a 772ER/77W, but they had to make a stop, did so in PVG. The plane could not fly the route going back to India w/o a fuel stop. Jet chose PVG hoping to pick up some of the us-china traffic.
This said, before it went belly up (to the bar?
) and the recession hit, Kingfisher announced that it was going to fly BLR-SFO N/S. They could do this as they had A340-500s they got cheap from Airbus. That plane has a range of 10,000 mi, and was at the time (and with the 772LR, range of 10,793 mi) the only aircraft with the legs for that flight in all conditions.
Its possible (someone would need to run the actual workable routing, there is lots of airspace blocked out on that route) that the 787-9 just might make it (its designed range is to be 9550 mi, if they actually hit that) but barring that possibility, West Coast to India flights are either going to have to be on a 772LR, have a tech stop going to India, or be ex-SEA or ex-YVR which makes the flight 600-700 miles shorter.
My guess is that West Coast to India routing will only happen once the 777-8x comes on line, it will have the range, and better fuel economy, to make these routes dueable.
You are welcome to think UA has a good rep in China and HKG, it does not. Ask any frequent traveler in either HKG or in a major Chinese City (PEK/Shanghai) and you will find that UAL has a very bad reputation. A series of bad cancellations with resulting riots at PEK and PVG basically tanked what little rep UAL had.
AA is retrofiting those A/C, and I'm not sure that a "very dated 772" with AA service is worse than a United "dream liner". In Y, I'll take the "very dated 772" on AA anyday over the cramped Y on the 787 on UAL.
United has a hub at LAX. CX flies to YVR(x2), SFO (x2), LAX(x4), ORD(x2), yyz (x1), EWR (x1), JFK (x3), all of these CX flights are on 77W or 747 A/C. If your explanation for why CX has 4 77Ws daily to LAX is CX is transferring the passangers to AA at LAX, I think you might want to rethink that.
p.s. and AA flies HKG-DFW on its own metal on the 77W.
the 789 would be perfect for EWR-BOM (or DEL), its a place that the 15% or so better fuel burn (over the 772ER) would make a very major impact on CASM at that range. At 9500 mi range, its also well within the 789s range.