Originally Posted by
vagabond
"The A350-1000 will, if Airbus is correct, produce an aircraft with lower seat-mile costs."
And there is the difference, Airbus has a miserable track record of actually delivering an aircraft that performs to it's design specification with respect to fuel burn. Boeing on the other hand "hits its numbers" or better right out of the box.
The current generation of airliners are marketed as lower operating cost (CASM) models, why not go with a sure thing?