lemira, welcome to our forum.

You are unlikely to get a flat bed, although an equipment swap makes it a possibility.

Have a search in the FAQ (top sticky thread in the CX forum), as well as the following link to get a sense for which aircraft serve which routes, and the lingo you can use to search the CX FT forum (773Z, 33K, 77H, 77G, etc.) http://flyerguide.com/Cathay_Pacific_(CX)_Fleet. Note that while longhaul routes rarely, if ever, have equipment swaps, they are more common on regional routes. So for CX504 or any flight you're thinking of changing to, bear that in mind.

If you want to spend some time getting to know CX search around here, there's a lot of info. The hard product in J on 773Z is known around here as CX's "new regional business class". It was rolled out somewhere around 2013-2014 IIRC. Search for variations on that and you'll get some more info about the hard product.

Overall, CX regional J is a product that quickly underwhelms the more you use it. Although JAL has that lay-z-boy looking thing, don't be fooled into thinking CX's regional J is a thoughtful product because it looks more modern.

Hard product negatives:
*Aisle access from the window seats requires climbing over your neighbor if they're reclined
*There's a middle seat on the 777 versions (777s are 7 across in regional J, whereas A330s are 6 across, avoiding the issue)
*Sleeping is very uncomfortable, worse than a lay-z-boy style recliner, due to the slanty, slide-forward design
*If you're tall, you will run out of legroom
*Limited to no under-seat storage, furthering the need for the window person to climb over the aisle passenger midflight

Hard product positives:
*Excellent power connectivity (both universal A/C plug and USB)
*Excellent AVOD - CX's complete "Studio CX". Blows JAL out of the water.
*Seats cannot recline into you (they are a "shell" style design)....which is also a negative, causing your seat's recline to be oddly uncomfortable and difficult for sleeping.

On the soft product, I haven't flown JAL short-haul lately so can't comment. But I have flown JAL long-haul lately in J, and it's fair to say they are miles ahead of CX long-haul J in the catering department. It's not even a contest. Combined with the fact CX J catering - including regional J - is mediocre at best, bad on average, and abominable at worst, my bet would be on JAL with the catering.