Some insight into why Magic Kingdom might have a higher score one day and a lower score on other days.

Most of the variation from week to week in October is due to school schedules and when schools take their fall breaks. Day to day vacation at the Magic Kingdom is driven by the Halloween parties. Party days have shorter hours and no fireworks. Most people will go to a different park with liberty hours. This makes the days without a party more crowded. You can get a lot done before 4 pm on party days. People with party tickets will start arriving at 4. If you have a park hopper ticket going to the Magic Kingdom on a party day is an excellent strategy. If you don't have a Hopper ticket and would stay late at the parks, you should avoid the party days. Using a Touring Plan will save you more time than just picking the day with the lowest crowd level. The extra ~5 hours would out way the lower crowd level.