I vote for KA, the aircraft doesn't really matter on a short-haul flight.
KA's A320s have an exclusive feeling as there are only 8 seats in J.
with 2 FAs(usually senior which translate to excellent service) dedicated to the cabin.
Food is a little bit better than CX on Chinese routes.
Premium Tea(Oolong and Jasmine Silver Fur) from Fook Ming Tong Tea Shop is served on KA as mentioned above.
I do think the A320s have better service due to FA-PAX ratio.
On the other hand the A330s have better entertainment system.
J seats on KA is enough for me to relax for a 2-hour flight.

CX
 

In my opinion, CX is better. I have flown both. As a foodie I think the food is also better on Cathay. Took a Lufthansa flight from Germany in January. Food was pretty awful.

Which if any are newer, better business class seats:

CX367 PVG 12:20 HKG 15:05 773
CX6853 PVG 12:50 HKG 15:35 321 (DragonAir)
CX6861 PVG 13:20 HKG 16:05 321 (DragonAir)
CX6835 PVG 14:20 HKG 17:05 330 (DragonAir)

So, it's a CX B773 vs. a KA A321 or KA A330? Best J seat (newer, more recline, etc.)?

Toss-up. Really doesn't make much of a difference at all, especially if CX's 773 is their "old" business class.

It's my opinion that you've said a bit of a paradox here if you want to split hairs....the "best" regional J seat on CX is actually their old one (you can tell that because it's controlled manually vs electronically. Differences are small but the "old" is definitely better). It's bigger and more comfortable.

Re KA, for the first two KA flights (presuming they stay as A321) they are large lazy-boy style seats similar to CX's "old" regional business class. The A330 can be either the KA lazy-boy seats identical to the A321 ones (which most likely would be a three class plane, with a six-row, two-section J class straddling the second exit doors), or it can be lie-flat style (which exists in one of KA's two-class configurations). Due to aircraft subs among KA's A330s it's fair to say you will have no control over that whatsoever - they swap A330 types on PEK and PVG routes almost daily. The one with lie-flat J class gives them more Y seats, and it stinks if you book Y because op-ups go down the drain when that config is swapped in (I think it's 33R, could be mistaken).

IMHO the food is considerably better on KA short hauls and I normally try to choose KA over CX where there is a choice.

However, if you prefer a guarantee of having some kind of inflight entertainment then CX is your choice.

I vote for Dragonair also!! Last time i flew KA was to PVG and Phnom Penh.The food and service is better than CX IMO. They also give u haggen dazs ice cream on flights to China even you are at Y class ;). But sadly no ice cream on HKG-Phnom Penh

Not for morning flights.

a recent comparison for me would give KA the edge...but this was on the 33L between HKG and BLR versus CX between HKG and NRT... but i enjoyed both much and had good service/food/booze both ways....as silly as it sounds, i actually like the KA FA's uniforms better...

Technically last time it was kind of in the morning as I took KA876 it departed as 10am well it was kina lunch anyway haha

I have to agree with the majority here. I personally find catering quality and cabin crews with KA to be superior to regional CX J. Unlike CX J (long or short haul), I've never had issues with KA's flight attendants.

I guess I have a minor preference for the "better" seat...right now, I am booked on KA805 tomorrow (Dec 3) which is an A330...how do I find out if it has the new lie flat J seats or old J seats?

i am not sure there is a way to know for sure...on my BLR-HKG it "should" have been a 33L but was subed at the last minute...having been in 10A...since there is a 10A on the 33R, i was not moved, however, those with BP's in rows further back were moved into the F section on the 3 class.....not I....

Hmm, this is showing a 330R, but I am in row 11. The seat may shows all business class eats are full, including row 1 and 2, and yet KVS is showing at least 2 C/J seats available. Do they wait and assign Rows 1 and 2 at the airport, or in advance.

Well, this 330 turns out to be a 3 class 330 sold as a two class, et voila, seems some or all of rows 1 and 2 were held back at the airport for airport check-in, and Qantas Emerald qualifies for an "upgrade" -- at least a seat upgrade.

Wonder why they didn't sell this as a 3 class flight, seeing that KA operates has 3 class segments on this route. Frankly, I don't care about F vs J food on this flight, as I had a full late breakfast at my hotel and am not planning on eating much on the flight...sleeping, maybe. ;) Thanks for peoples' advice.

OK, local geniuses...now what about the difference in J seats on CX HKG to PVG on A343 versus B773, assuming the equipment stays the same?