It's not that simple, and frankly airline company is not near the top of my list of relevant variables.

When I fly, my primary goal is to maximize my chances of arriving close to on time. As such, I tend to gravitate towards the market leader(s) on any given route. So, in the case of PEK-SHA, I only consider CA, FM, and MU because CZ and HU are comparatively week; if their flights are delayed or cancelled, I'm likely SOL.

Secondarily, I look for 737s when I'm flying in Y (fast boarding/deboarding) and 330s/340s when I'm flying in C (because they tend to be really nice, regardless of airline).

Third, I dislike bus gates and try to avoid them whenever possible (at least wrt to departures; bus gates inbound are often a good thing because you get dropped off near baggage claim... PEK T3 is a notable exception).

Forth, speaking of PEK T3, I go out of my way to arrive at PEK T2 because the drill is twice as fast and there is considerably less walking.

Finally, all other things being equal, I go with CA because I like BMI miles (in A/D/C/F, the earning multiplier is pretty sweet). Apart from that, I basically have no loyalty at all (apart from my reverse loyalty to CZ; while many people like CZ, I find their customer service to be atrocious, even wrt Chinese standards).

ETA: KN is worth checking out ex-BJS because they are the only carrier operating out of NAY and they are owned, in part, by the PLA (a frequent cause of delays for other airlines), but the service is spartan in both Y and F.