I know CX is the internationally renowned one of the pair, and KA is the little sibling barely known outside China, but on my weekly travels between PEK and HKG, on which both airlines fly, I have consistently found the KA service and experience superior.

Why:
- 2-4-2 cabins in Economy as opposed to often 3-3-3 on CX
- Almost always get a visit from the purser in economy as OW Sapphire, less than 50-50 on CX although some crews on both are excellent
- Better food options in both cabins. In KA the dim sum breakfast and the meal trolley during the day always seem excellent. By contrast, when travelling economy on CX a couple of weeks ago i picked up a business menu while waiting to get off and noticed the options were identical to the economy meals
- Haagen Dazs on KA (I'm easily pleased I know)
- KA crews better equipped to deal with what we might call the inexperienced travellers on mainland routes, compared to a sometimes snooty approach which doesn't work in CX

For me the only plus side of CX is the availability of Premium Economy (which is often empty) on one of the daily rotations.

Would be interested in what others think?