I think at the end of the day ( in all seriousness ) the T and Cs pretty much even out between the 2, the big advantage with HKA is 15% bonus after 3 years.
Drivers from both airlines think their airline will be the next biggest thing, the only thing I can say which is concrete is that HKA have more than double the A/C than HKE,with 2 more definitely arriving early next year, and HKA are the ones who's name has been put to the Airbus order, other than that its all rumour and inuendo.
The only benefit of joining HKA was the easy going interview process, no sim, no tech quiz, thats now gone. If you are going to go thru all that you may as well do it with cx/ka. Especiall with KA now getting more desperate for drivers.