The AP polls pick the voters mostly based on where the big cities are with the big newspapers ... which happens to be mostly in BigTen and ACC country. They also have voters from big name programs ... which happens to be BigTen and SEC conferences. SO, there are more voters in the AP poll from the BigTen / SEC / ACC, which means those teams tend to do a bit better.

Similar effect in the coaches poll.

So, yes, BigXII teams will not do as well as ACC teams in the polls because of the way the polls are structured / populated.