You may want to check with CX to see if your route is scheduled to have new J or current J (and of course make sure it's a long-haul flight). Huge difference between current J and new J.

I flew that in April just to try the 787. It's a wonderful plane, and I really noticed and enjoyed the higher air pressure and humidity. I loved the special menu items and excited signs all over. And of course JL has the nicest J and F lavatories. However, the current J seat is disappointing: paired angled ("wedgie") seats. Too bad the newly-announced new J is only for the 777-300, not the 787 (as far as I know). A superb plane needs a superb seat!

To your main point (which F to choose), you'll find lots of different opinions, and in part this is because each of us finds different aspects to be more or less important. Asian carriers tend to have much more consistent and professional service (which some find delightful and others find annoying), while U.S. carriers tend to have more inconsistent and casual service (which some find warm and genuine and others find sloppy and borderline rude). The AA F seat is quite nice, in that it provides significant personal space, lots of usable space, plenty of storage, lots of surface area, etc.

The JAL SKY SUITE on 777-300ER is just the first rollout. JAL has plan for upgrading products on other planes as well. 767-300ER upgrades will come mid next year and they are studying for the 777-200ER too. Although they haven't publicly commented on 787-8 and 787-9, but you bet those planes are on their radar as well esp with the 787-9 which they haven't finalized the cabin interiors yet.