Actually it's better for the underpair if it's further away from the overpair. The underpair needs to suck out, so it benefits more from having the straights unblocked.
KK vs. AA is 17.8% if you average all the different suit combos. 77 vs. AA is 19.4%.
Re: that was the worst
KK vs. AA is 17.8% if you average all the different suit combos. 77 vs. AA is 19.4%.