I'm curious why you are using a Ultra high performance tire on an SUV.
Further, why you would think a decrease in traction (560 AA A to 540 A A) is the right direction for your son. (I'm ignoring the 20 unit drop in treadwear rating.)
Wouldn't the Conti Control Contact Tour A/S Plus be a better choice? (700 A A)
Fitment is 235/50/18, the tire you mention is not made in this size. That said I agree with you on the traction point. DT guy said their version would last longer but the numbers seem to say otherwise.