Try Cathay Pacific they have one of the best customer services in the world.
Don´t even try Japan Airlines. On August 2000 I flew NRT-MEX in JL and in business class and it was the worst flight I´ve ever been. The seats can´t recline to a decent position. The food is not that good and they no longer give you amenity kits.
If you can´t get CX go for UNITED, they have a great business class. On the 744 try the upper deck, but you´ll be flying a 772 from NRT-BKK
I too would go for CX! UA is a decent airline but CX is far better. As for JAL I agree that the C Class needs new seats, though the food I thought was very good on JAL! Go with CX, you will not be dissapointed!!
Although JAL is putting in new C-class seats as well as F-class, forget it! JAL's FA and overall service has dropped significantly and you will be disappointed.
Try CX as they have one the greatest services in C-class. I have always been pleased with them.
If you do have a chance, try ANA. They too are excellent.
Cathay Pacific! They are one of the best airlines in the world, second only to Singapore Air in my opinion. I am jealous you have the oppertunity to fly them; but I strongly suggest you do choose them, as they are miles above UAL, and better than JAL.