It really depends on where you are going. If you primarily fly between NYC and the west coast/Florida, JetBlue would make a great choice.
But if your travels take you to the heartland, mountain west or any smaller city throughout the country then B6 isn't going to get you there very efficiently/conveniently. European/Asian travel on B6 isn't going to happen either (though they do have code-share agreement with EI I think).