I would think there is some minute difference that would make sets more feasible with lower cards... reason I say that is you can only hit a set if you see a flop... flop play is only possible against an opponent... oppnents are not likely to play crap... so since they are playing better cards, that reduces the number of available better cards in the deck minutely... thus I would think you might see a set of 8's maybe like .05 percent more than a set of Ks.
But I never took statistics.