It's a combination of the two. In the beginning, the preseason polls are supposed to rank the 25 best teams. As the season goes on, the polls should become more and more about performance and less and less about predictive power. The final poll should have nothing to do with ranking the teams and everything to do with how well they performed.

By this point in the year I think they should be mostly about performance on the field. If anyone thinks that Florida isn't one of the ten best teams in CFB, then that person is an idiot. But there are >10 teams who have accomplished more than them so they aren't there.

Edit: I'm not saying just rank the teams by their records. If Team 1 is 5-1 against all Top 25 teams and Team 2 is Hawaii then Team 1 has accomplished more than Team 2.