In my mind I rank them as follows:

AF, KE, KL, OK, AM, CO, then a gap to NW, then a yawning chasm to AZ and last (and definitely least) DL.

Sample size for my rankings are at least 8 sectors on each carrier with the exception of AM (2) and OK (3). I'm reasonably happy flying any of the first 6, happy enough on NW (although please bring back the A330 into London and give those venerable DC-10s the rest they deserve) but will lie, cheat and feign illness to avoid AZ and DL which, I believe, should both be allowed to die off.

Wouldn't you know it, but all my status is on DL. Doh!