The choice here is ultimately going to be driven by availability, although there are plenty of airlines worth checking given the miles that are available.
Consider that it’s entirely possible to use a different airline for the outbound as the return — not just to try different products, but because schedules and availability may differ, especially for an outbound to North Asia and a return from Southeast Asia.
I’d generally rank the first class products of airlines flying from the US West Coast across the Pacific as follows: