Neither ANA not JAL offer much in terms of perks for their own top frequent fliers when in Y. You may get a greeting before take off, and you are in the pecking order for op-ups but that is about it.

ANA used to offer PY upgrades at check in, but that has been monetised away. They are running a campaign right now as the last part of the free upgrades, but rather soon it will be history.

There are so many Diamond members (both ANA and JAL) that doing anything really special for them is not really possible.

In terms of switching to one of the programs, I would say they are only good if you can make Diamond. The Super Flyers Card, or JAL Global Club are neat ways of keeping status. Ut part of the reason why status holders in Y get nothing more than lounge access.