One company already has the tooling, the jigs, the plans, the machinery, the buildings, the resources, the management, and the employees ready to go to work tomorrow. The other company is all on paper and will take several years to fully man up.
p.s. the 330 MRTT has been flying since last fall (October?) and GB, the Aussies, Emirates, and the Saudis have all ordered it.
One company has the factory, but no plane yet. (They only submitted the KC-767AT proposal in April 2007)
The other has no con-US production facilities yet, but already has the first aircaft for the US contract in the air (maiden flight was in September 2007) The first KC-30 tanker aircraft, the D-1, completed its maiden flight, lasting four hours, on 25 September 2007. D-1 will be the first aircraft delivered to the US Air Force if the Northrop Grumman-led team is awarded the KC-X contract.
Northrup-Grumman will probably have the factory up before Boieng could have worked the bugs out of the bew version of the KC-767.