Head to head, the Airbus 319/320/321/330 cannot compete with the Boeing family of aircraft, in reliability, performance, fuel economy, or resale value. Sure, the initial cost of ownership for Airbus fits in with the modern day airline model of short term balance sheets, but total cost of ownership is far better with Boeing on a long term basis.
Oh, and let's not forget that US often has to make a fuel stop in ABQ for their "non-stop" transcontinental service to PHX from PHL, PIT, and DCA during the winter months because the Airbus 320/321 can't make it on one tank of fuel. Put a 757-200 on those routings and you could make it to LAX, and then fly on to PHX without adding fuel.