Rob-
Amen- It isn't about the pricing objections. But what I can't stand is how these vendors are constantly trying to win influence of consumers (Autotrader's trade-in value and the new Carfax fiasco) illustrate to me their marketing departments may not be hitting on all cylinders. The dealers are the ones who pay their bills, and they need to be finding ways to strengthen those relationships, not trying to win over customers (I realize Carfax's success is largely predicated on being branded as the de facto vehicle history check).
I have been with dealers who have used either system, and for me, the Autocheck scoring system is probably the strongest argument for a premium price for your vehicle when it scores higher than the average vehicles.
As one earlier comment pointed out, customers may ask for the Carfax, but when showed Autocheck, and the differences explained, I have never had a customer decline the Autocheck.