re: Which airline has the best rewards program for domestic travelers?

Delta has been the best airline in recent years, so they can get by with having a less rewarding frequent flier program. United is next. AA and Southwest are crummier airlines, so they have to offer more rewards as an incentive.

It's highly unlikely that it will make sense to travel on just one airline. The flights will be at inconvenient times or randomly cost too much, etc. -- and the rewards aren't that great.

But I do agree with the idea of making Southwest the default and using another airline for when Southwest isn't convenient or doesn't work well (probably AA, due to the number of destinations). Y'all might even look at destinations and plan to get an airline credit card or two now, to get free bags, etc.