I've flown both. ANA's first soft product beats JAL's Business Soft product. Also ANA's mattress is one of the best you can have on an airline. I wanted to buy one for my car after the flight because I slept so good, but they retail at like $1k or something ridiculous for such a small pad.
So I say go ANA first if you value sleep.
Also, JAL's 777 flights cabin temps seem to run a little warm. Didn't have that issue on ANA.