Strategy page blog has a posting about the Airbus-Boeing competition. Boeing plans to contest the contract award. The Air Force is buying existing airliners, the Boeing 767 vs the Airbus A330. Both planes have been in production for years. Cost to buy, to operate, range, payload, and everything else is well known. There is no research and development money or risk, there is no logistics support, parts and service are widely available on the civilian market.
Airbus offered a larger plane. Boeing could have offered their larger 777 transport if they had been asked, or if they thought it was more appropriate to the mission. Or Boeing could have offered both aircraft and let the Air Force decide which size fits all.
Domestic content of the two planes is not all that different. The Airbus plane has American engines and a lot of American made parts in it. The Boeing plane has major subsections built over seas.
Air Force supplied reasons for the Airbus win boil down to the larger plane was more cost effective, could supply more fuel with fewer flights, which is pretty obvious. Air Force has not released the vital bid costs. Both aircraft are well proven, widely sold, commercially successful jet liners. Either would do a fine job as a tanker. Air Force should select the lower cost aircraft. So far, we don't know which plane was lower cost, the Air Force has not released the cost data.
Expect a long drawn out contest of the contract award, with plentiful fees for lawyers.