I haven't looked into JetBlue or Virgin America, but a big part of why I use Southwest over others simply due to their frequent flier program. I take a flight

I haven't looked into JetBlue or Virgin America, but a big part of why I use Southwest over others simply due to their frequent flier program. I take a flight from SF to LA about once a month, meaning I can spend as little as $1,300 to rack up enough credits to get a free round trip, which I use on flights to the east coast that would have cost me $400.