tough question. My first reaction is probably kxx because more people are calling (and not repumping) with KQ, KJ, K10s than with AQ, AJ . I think it's pretty close. I think I go with Axx in the end though for the reasons stated above and because people with KQ on an K high flop can put AA into your range as well as AK whereas on an ace high board they're only worried about AK (ignoring coolers). Not sure if any of this makes sense.