Now that there are only 3 "majors" in the US, comparing them is less accurate.
Can we expand the pool to "all non LC carriers" or "all global carriers"? With the rise of WN, B6, VX, etc and the additional routes by asian, european and ME carriers, does it make sense to compare the 3 majors in isolation? How many folks when booking a trip to anywhere (either LHR or LAS) compare only the 3 US majors? I suspect this trend will continue over time, esp if we get another startup airline or more open skies agreements.
Mergers followed by capacity cuts are making the 3 majors less and less relevant. In many cases the trend setters are someone else.