Short answer is yes far better.

9 across on 777, 8 across on 787. 34" pitch. Food is of course always open for debate, but quality is definitely higher in JAL. But taste can be debated. No real cuts in service during pandemic for JAL. Basically business as usual for service.

I am not sure what mean with not being able to accrue miles. As Alaska is a member of Oneworld now, the issuing carrier should not matter, and operating carrier JAL and AA flight number if that is what you are thinking of, is also fine.