Welcome to FT, Flying Trojan

There are currently two different J-class products fitted on Cathay's long-haul aircraft. Both are configured in a herringbone pattern.

The majority of long-haul aircraft (all 744s, all 343s, most 77Ws, most 333s) are still fitted with the older product, which was rolled out in 2007, if I remember correctly. This older iteration is code-named 'Olympus' and is marked by narrower seats and high dividing partitions, earning it the unfortunate nickname of 'the coffin' for its lack of width. Olympus seats are angled away from the window and towards the aisle. Middle seats are angled away from each other.

Cathay announced a new J product in December last year. You'll see this referred to in the FAQ thread of this forum as "Cirrus." Cirrus seats are mostly seen as a vast improvement upon the old product - they are much wider; 'A' and 'K' seats actually face the window, while the middle seats are angled towards each other, making it more suitable if you are travelling with a partner. The "New Business Class" profiled on the CX website is Cirrus.

LAX is serviced by the 773-300ER. However, only 7 (at last check) out of 24 of these aircraft are currently fitted with Cirrus. The idea is that the 4 daily rotations to JFK receive Cirrus before (the increasing number of) Cirrus aircraft get deployed to LAX and LHR (the next ports in line to receive the product). In practice, due to CX's tendency to switch aircraft around a lot, many other ports have already seen the new product (albeit infrequently).

This is all to say - you can't by any means be sure of getting a Cirrus aircraft out of LAX in November. Still, having said that, LAX-HKG is one of the longer segments on the CX network and their Y seat is super-uncomfortable. I'm not sure if you've flown on CX since the new product was introduced. But if not, it's a fixed shell, meaning that instead of reclining, the seat cushion slides forwards, generating a large gap between the cushion and the backrest. Even on shorter flights, it is enough to give you back ache.

So however nice CX F is, I would take the two segments in J any day, just to avoid Y. Another reason to do double-J is that the LAX-HKG segment is significantly longer, and this is the sector you say would be in Y. But that's just me. I'm sure that if you CAN tolerate 15 hours of Y, the F product will not disappoint.

Good luck!