So, so even Business class
I’ve been flying TPAC for @ a decade. Mostly business class. I’ve usually flown. SEA-PVG leaving midday SEA time. Never slept well in the 767 (Delta). Recently I’ve started flying SEA-TPE on EVA and their flights leave after midnight SEA time. Even in just Premium Economy I found I could sleep many hours more than I had in Delta Business class.
I assume the the difference is flying during my normal sleep time.
It it also helps to have noise cancelling headphones.