Originally Posted by pbarnette

I largely ignore the rankings not because they aren't objective, but because there simply isn't enough differentiation between the carriers for it to influence my decision-making.

I've posted this before, but look at mishandled baggage as an example. DL has 5.02 mishandled bags per 1000 pax. CO has 2.89. Dramatic difference, huh? But put this into perspective. Let's assume that a mishandled bag causes you $1000 worth of inconvenience. This means you should pay just over $2 extra to fly CO on the exact same routing and timing. The difference is almost certainly not worth trading a non-stop for a connection or a lesser time, as you would eat up the $2 difference after about 5 minutes of your time wasted.

Delays would see similar arithmetic, once you exclude those air traffic and weather delays - it may lead you to choose different airports, but I doubt it would inform your choice of carrier. Denied boarding rates are so low at all carriers as to not be worthwhile to look at. Complaints? Unless I am the one complaining, I'm not really concerned.

Are these measures objective? Yes. Do they actually give you any real, actionable information? Not in my opinion.