Rather like apples and oysters, these two. Both do CAS but in very different ways. It seems like test parameters could easily be skewed to give one an advantage. Also, the A-10 has the home team advantage because of more mature tactics/doctrine. In any event, it seems silly to choose one over the other as they have such different roles.
Then again, the USAF is looking for any excuse to kill the A-10. Sadly, the A-10 is dying because it bridges the Air Force and Army and neither side wants to pay for it; each claims it belongs in the other's bailiwick. The Warthog is too good a plane to lose to infighting; they should just bring back the Army Air Corps and be done with it.
"On 4 November 1952, a memorandum of understanding (MOU) was signed between United States Air Force Secretary Thomas K. Finletter and United States Army Secretary Frank Pace that removed the weight restrictions on helicopters that the U.S. Army could use. It also widened the range of tasks the Army's helicopters could be used for. However, it also created an arbitrary 5,000 pounds weight restriction that limits the Army's ability to fly fixed-wing aircraft. As a result, the U.S. Army today is dependent upon the U.S. Air Force to purchase and man fixed-wing ground-attack aircraft to fulfill close air support missions."