As someone who's flown both HND-LAX and NRT-SEA in J (approximately the same distance/flight length), I wouldn't describe the service for HND-LAX as necessarily "reduced," except for the fact that that flight still uses the old angled-flat J configuration.
All told, if you have no choice but NH angled and AC herringbone, I would say you should go for the latter...unless you want to experience J service with a Japanese flare, in which case NH is an obvious choice, even in the old configuration.